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LIBRARY 

UNIVERSITY  OF  CAUFORJHIA 

DAVIS 


CAIvlKORNIA   STTATTK    IVIININO   BURKAU 

J.  J.   ORA"WPORt>,   State  Mineralogist. 


BUivLKTiN    No.    S.  San  Francisco,  June,  1894. 


METHODS 


MINE  TIMBEEING. 


By  W.   H.   storms, 

Assistant  in  the  Field. 


SACRAMENTO: 

STATE    OFFICE,      :       :       :       A.    J.    JOHNSTON,    SUPT.    STATE    PRINTING. 

1894. 

LIBRARY 

UKIVERSITY    OF    CALIFORNIA 

DAVIS 


PREFACE. 

There  is  no  attempt  in  this  Bulletin  to  present  a  complete  treatise  on 
methods  of  mine  timbering,  but  simply  to  give  consideration  to  those 
systems  ordinarily  used  in,  or  adapted  to,  the  gold  mines  of  California. 
Both  in  the  lode  and  deep  gravel  mines  of  this  State,  those  systems  in 
use  have  been  selected  from  the  best  practice  and  applied  in  various 
ways  according  to  circumstances.  In  collecting  the  material  herewith 
presented,  many  mines  have  been  visited  and  the  details  of  timbering 
work  noted,  so  that  those  who  have  not  an  opportunity  of  comparing 
methods  for  themselves  may  be  enabled  to  learn  the  practice  of  others. 

It  has  been  thought  proper  also  to  give  some  detailed  account  of  sys- 
tems of  mine  timbering  used  in  other  States  where  extensive  ore-bodies 
are  worked,  since  these  are  adapted  to  use  here  under  corresponding 

conditions. 

W.  H.  STORMS, 

Assistant  in  the  Field,  State  Mining  Bureau. 


METHODS  OF  MINE  TIMBERING. 

By  W.  H.  Storms,  Assistant  in  the  Field. 


The  excavation  of  any  considerable  amount  of  earth,  or  rock,  beneath 
the  surface  of  the  groun'd  usually  necessitates  that  the  roof,  and  not 
infrequently  the  sides,  of  such  excavation  be  sustained  artificially  to 
prevent  caving.  In  these  later  years  the  size  of  underground  excava- 
tions is  so  great,  as  compared  with  those  formerly  made,  that  the 
ingenuity  and  skill  of  the  miner  is  taxed  to  the  utmost  limit.  So  suc- 
cessful, however,  have  miners  become  in  devising  novel  methods  to  meet 
daily  exigencies  that  the  obstacles  usually  encountered  in  mining, 
among  which  are  flakey  rock  roofs;  soft,  running  ground;  floods  of 
water,  sometimes  scalding  hot;  and,  worst  of  all,  swelling  ground  with 
heavy  pressure  from  all  sides,  including  the  bottom,  have  mostly  been 
successfully  overcome. 

Before  Deidesheimer's  "  square  set "  system  came  into  use,  the  ingen- 
ious placing  of  posts,  caps,  and  ^'  stulls  "  constituted  the  only  method  of 
timbering,  the  multitude  of  conditions  met  in  the  mines  making  the 
combinations  almost  endless.  Where  veins  occur  in  firm,  solid  rock, 
being  perpendicular,  or  near  it,  the  danger  of  caving  is  greatly  lessened, 
and  the  amount  of  timber  required  is  reduced  to  a  minimum,  but  these 
conditions  are  exceptional. 

Veins  dip  at  all  angles  between  perpendicular  and  horizontal,  and 
vary  greatly  in  width.  Moreover,  the  character  of  the  wall  rocks,  as  well 
as  of  the  ore  itself,  is  so  variable  that  unexpected  problems  are  encoun- 
tered daily.  The  shape  of  large  bodies  of  ore  is  a  matter  of  great  impor- 
tance in  determining  the  system  of  timbering  to  be  employed. 

Through  all  this  variety  and  change  in  form,  dip,  size,  and  character 
of  the  vein,  or  deposit,  and  in  the  inclosing  walls,  certain  established 
principles  are  followed  in  sustaining  the  roof  and  sides,  the  constant  aim 
being  to  prevent  caving,  and  to  avoid  such  a  catastrophe  timbers  are 
placed  with  a  view  of  holding  the  rock  masses  in  place,  and  always  in 
such  a  manner  as  to  receive  the  strain  directly.  Those  timbers  which 
reach  from  wall  to  wall  of  an  inclined  vein  (stulls)  are  not  set  at  a 
right  angle  to  the  pitch  of  the  hanging  wall,  but  at  a  somewhat  higher 
angle.  The  reason  is  obvious,  for,  if  placed  at  a  right  angle,  should  a 
subsidence  of  the  wall  occur,  the  timber,  partaking  of  this  movement, 
at  its  upper  end,  would  then  have  a  tendency  to  fall  of  its  own  weight, 
whereas,  if  set  originally  above  an  angle  of  90  degrees  with  the  hanging 
wall,  the  subsidence  of  that  wall  only  serves  to  wedge  and  hold  the 
timber  support  more  firmly,  when  it  must  bend  and  break  before  falling. 
When  properly  placed,  stull  timbers  usually  give  sufiicient  warning  of 
their  weakness  to  permit  of  placing  additional  timbers  and  subsequently 
the  removal  and  replacement  of  old  or  weak  timbers. 

To  make  an  understanding  of  the  various  practices  more  comprehen- 
sive a  number  of  drawings  have  been  introduced  in  this  article.  As  a 
matter  of  course  certain  exigencies  are  likely  to  arise,  the  character  of 


—    6    — 

which  has  not  been  anticipated,  but  in  all  cases  the  principles  applied 
remain  the  same,  and  it  is  thought  that  the  conditions  most  likely  to 
occur  have  been  treated  fully  enough  to  meet  the  demands  of  metallifer- 
ous mining  generally. 

KINDS    OF   TIMBER   USED. 

In  some  instances  solid  masonry  is  built  to  sustain  certain  portions  of 
mines,  and  in  late  years  iron  has  been  introduced  as  a  substitute  for 
timber,  but  in  American  mines  timber  is  most  commonly  employed. 
Ordinarily  the  location  of  the  mine  determines  the  kind  of  timber.  Pine 
of  various  kinds  is  more  extensively  used  than  any  other.  Sugar  pine 
and  spruce  are  preferred  when  obtainable,  but  yellow  pine  is  by  far  the 
most  common.  Oak  is  gladly  taken  when  good  sticks  of  sufficient  size 
can  be  found.  There  are  oak  timbers  in  mines  in  Mariposa  County, 
apparently  sound,  that  have  been  in  place  for  twenty  years.  They  cer- 
tainly outlast  any  other  timber.  Cottonwood  and  redwood  are  some- 
times used  when  no  other  is  obtainable,  but  are  not  at  all  desirable.  In 
the  desert  in  this  State,  in  parts  of  Arizona  and  Nevada,  miners  take 
any  timber  they  can  get,  even  resorting  to  the  yucca,  which  answers 
quite  well  for  a  time  in  that  dry  climate,  when  the  pressure  is  not  too 
great.  At  Silver  Reef,  in  San  Bernardino  County,  green  yuccas  were 
used  in  timbering  a  drift.  They  still  stand  in  fair  condition,  having 
been  in  place  five  years.  The  Superintendent  of  the  Gover  Mine, 
Amador  County,  California,  has  commenced  some  experiments  with 
spruce  and  sugar  pine,  placing  them  side  by  side  in  the  same  set  in  the 
lower  levels  of  his  mine,  to  test  their  durability. 


Fig.  A. 


TUNNELS   AND    DRIFTS. 

The  methods  employed  to  sustain  the  roof  and  sides  of  tunnels  and 
•drifts  are  numerous,  the  existing  conditions  determining  the  method. 
Often  the  rock  is  sufficiently  firm  to  stand  without  timber,  but  at  times 
the  conditions  are  annoying  and  dangerous. 

Where  the  pressure  is  entirely  overhead  an  upright  post  is  set  on 
either  side  of  the  tunnel,  usually  spread  somewhat  at  the  bottom,  but 
otherwise  always  at  right  angles  to  the  roof.  (Drifts  are  frequently  run 
on  an  incline,  particularly  in  blanket  veins,  and  also  in  fissures  having 
a  low  angle  of  dip.)  (See  Figs.  2  and  4.)  On  these  posts  are  placed  a 
cross-piece  called  a  cap. 

"When  it  may  occur  that  the  floor  of  a  tunnel,  drift,  or  cross-cut  does 
not  afford  a  firm  foundation  for  the  posts,  as  in  soft,  wet  fissures,  when 
not  in  ore,  or  as  is  often  the  case  at  the  entrance  to  a  mine,  a  cross-piece 


I      I     I      I  A-i  «  I  tt      I      I      I — r 


ENTRANCE     TO     TUNNCL,    CALAVERA*     COWSOLIOATTO    MINE, 
CARBON     HILL,     CALAVERAS     CO^        CAL- 


or  sill  is  first  laid  and  the  posts  set  upon  it.  A  second  cross-piece  (the 
cap)  is  then  inserted  at  the  top,  the  ends  resting  upon  the  posts,  the  cap 
being  employed  in  all  cases  whether  the  sill  is  necessary  or  not. 

In  working  ground  that  is  fairly  firm,  particularly  in  the  drift  gravel 
mines  of  California,  a  system  of  posts  and  "breasting  caps"  is  used. 
This  consists  of  a  piece  of  timber,  hewn  or  split,  2^  feet  long,  1  foot  wide, 
and  3  or  4  inches  in  thickness  (the  cap),  which  is  placed  against  the 
roof,  and  a  post  of  the  necessary  length  is  set  beneath  it,  being  driven 
into  a  perpendicular  position  by  blows  of  a  heavy  hammer  or  maul.  It 
is  a  cheap  and  secure  method  of  timbering  small  drifts,  and  is  often 
employed  in  large  ones,  the  breast  extending  entirely  across  the  channel. 
Lagging  placed  at  right  angles  to  the  cap  may  be  driven  in  above  it  when 
necessary. 


—   8   — 


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9    — 


Very  often  pressure  is  exerted  from  the  sides  as  well  as  from  the  top 
of  a  drift.  In  such  cases  the  timbers  are  framed  with  a  view  to  binding 
them  more  firmly  together  when  in  place.     (Fig.  8.) 

Figs.  1,  2,  3,  and  4  show  several  styles 
of  framing  timbers  for  drifts.  Of  these 
Fig.  4  is  undoubtedly  the  best.  Better 
than  any  of  these  is  the  beveled  notch, 
which  greatly  reduces  the  liability  of  the 
timbers  splitting.  It  has  come  quite 
extensively  into  use  of  late  years.  When 
properly  framed  and  set  there  is  little 
danger  of  slipping.  Still  another,  and  no 
doubt  the  best  method  of  all,  has  lately 
come  into  practice.  It  is  that  of  nailing 
a  2-inch  plank  on  the  under  side  of  the 
cap.  By  this  device  the  fullest  strength 
of  the  timbers  is  obtained,  with  no  proba- 
bility of  splitting. 


THE  BEVELLED  NOTCH 


Fig.  9  A. 


•  When  round  timbers  are  used  they  should  always  be  stripped  of  the 
bark  or  they  will  speedily  decay.  The  manner  of  framing  timbers  is  the 
same,  whether  they  be  round,  hewn,  or  sawed. 


—  10  — 

Figures  5  and  6  show  a  method  of  placing  posts  and  caps.  It  is 
seldom  seen  now.  There  is  nothing  about  it  to  recommend  it.  Oak  is 
the  only  timber  that  may  be  safely  employed  in  this  manner,  pine  being 
too  soft  and  quite  certain  to  split. 

Where  one  side  of  a  drift  only  and  the  roof  need  support,  the  post  and 
cap  (Fig.  7)  is  sometimes  employed,  One  end  of  the  cap  rests  upon  the 
post,  the  other  on  a  shelf,  or  niche,  cut  in  the  opposite  wall. 


USa  ft.  LEVCl 
AMADOR      Co, 


LAGGING. 

When  the  roof  or  side  of  a  tunnel  is  loose  and  shows  any  tendency  to 
cave,  sprawl  off,  or  run,  lagging  must  be  employed.  Lagging  is  the 
name  given  to  strips  of  wood  4  to  6  feet  long,  6  to  8  inches  wide,  and  2 
to  2i  inches  thick.  They  are  usually  split  from  pine  logs,  but  sometimes 
2-inch  plank  6  inches  in  width  is  substituted.  In  large  shafts  in  heavy 
ground  3-inch  plank  is  sometimes  employed.  The  methods  of  driving 
lagging  are  shown  in  Figs.  10  and  12.  The  pieces  of  lagging  are  inserted 
over  the  top  of  the  cap,  the  ends  pointed  upward  a  few  degrees.  They 
are  driven  forward  as  the  work  of  excavation  progresses,  when  there  is 
danger  of  caving.  Not  infrequently  ground  will  stand  for  many  hours 
and  sometimes  for  months  before  caving,  but  it  is  cheaper  to  timber  very 
soon  after  the  excavation  has  been  made,  in  order  to  keep  the  ground  in 
normal  condition,  giving  it  no  chance. 

The  two  systems  shown  in  Figs.  10  and  12,  while  the  same  in  principle, 
differ  materially  in  detail.  In  Fig.  10  the  lagging  is  inserted  between 
two  caps  which  are  separated  by  wedge-shaped  blocks,  one  of  which  is 
placed  in  the  center  and  one  at  either  end.  (See  between  A  and  C,  Fig. 
11.)  The  lagging  is  driven  forward  as  explained.  If  the  ground  is  very 
heavy  a  '* false  set"  (Fig.  12)  is  set  up  and  the  ends  of  the  lagging  rest 
upon  it.  The  excavation  progressing  and  the  lagging  being  driven  well 
forward,  the  next  set  is  put  in  position  and  the  lagging  driven  ''  home," 
that  is,  until  the  forward  ends  find  a  secure  resting  place  on  the  true  set. 
The  false  set  is  then  knocked  out  and  the  same  procedure  gone  through 
with  the  next  set. 

The  only  difference  between  Fig.  10  and  Fig.  12  is  that  in  the  former 
there  are  two  caps,  as  explained  above,  while  in  Fig.  12  the  lagging  is 


—  11  — 


—  12  — 

inserted  beneath  the  forward  ends  of  the  next  set  back.  In  each  case 
the  lagging  is  kept  pointed  slightly  upward  by  the  insertion  of  a  block 
of  wood  shown  at  B,  Fig.  12.  When  the  forward  ends  of  the  lagging 
rest  on  the  false  set  this  block  may  be  allowed  to  drop  out.  The  system 
shown  in  Fig.  10  can  be  employed  much  more  advantageously  and  work 
progress  more  rapidly  in  very  heavy  ground,  than  when  that  shown  in 
Fig.  12  is  used,  which  does  very  well  in  lighter  ground.  Where  the 
ground  is  very  bad  the  lagging  must  be  kept  driven  as  far  forward  as 
possible.  By  observing  care  in  this  matter  serious  runs  are  sometimes 
prevented.  Sills  are  only  employed  when  the  bottom  of  the  tunnel  does 
not  afford  a  firm  foundation  for  the  posts. 

For  lagging,  spruce,  yellow  pine,  and  tamarack  are  much  used,  but 
the  sugar  pine  of  California  has  no  superior  for  toughness  and  durability. 
Lagging  should  not  be  too  strong,  for  in  the  event  of  extreme  weight 
it  should  bend  and  give  notice  of  impending  danger.  The  miner  may 
then  relieve  the  pressure  by  cutting  away  a  portion  and  reinforcing  the 
timbers,  thus  saving  the  more  expensive  framed  timbers  and  perhaps 
preventing  a  serious  cave. 

Caps  and  posts  are  all  sizes  from  4x4  or  4x6  inches  up  to  24x30 

inches,  according  to  the  size  of  the  ex- 
cavation and  the  character  of  the 
ground.  Caps  should  be  free  from 
knots  and  checks  as  far  as  possible. 
Less  care  is  necessary  in  the  selec- 
tion of  posts,  though  all  timbers  should 
be  of  good,  sound  wood.  Sills  extend 
somewhat  beyond  the  posts  which 
POST  AND  SILL  JOINT  ^^^^  ^^^^  ^^^^^^     A  shallow  notch  is 

usually  cut  in  the  sill  to  admit  the 
post,  the  bottom  of  which  is  cut  at 
right  angles  to  its  sides.  (See  the  ac- 
companying figure.) 

The   greater  care  taken  in  framing 
and  setting  up  mine  timbers  the  less 
Fig.  13  A.  danger  there  will  be  of  collapse  in  the 

future.     The  tools  necessary  to  secure 

this  exactness  are  a  plumb-bob  and  a  steel  square.     A  spirit-level  is  also 

very  useful. 

TRACK-LAYING. 

To  construct  a  track,  cross-ties,  made  of  3x4  scantling,  are  often  laid 
on  the  floor  of  the  tunnel  or  drift,  and  to  these  are  spiked  "T"  rails. 
When  flat  iron  is  preferred  a  durable  track  for  permanent  use  is  made 
by  setting  long  2x4  scantling  in  slots  sawed  in  the  cross-ties,  the  long 
strips  being  secured  by  driving  in  wedges  at  the  side.  The  details  of 
track  construction  are  shown  in  Figs.  A,  Al,  A2,  A8,  and  A4,  which  are 
on  the  same  plate  as  Figs.  1  to  9.  Upon  the  scantling-stringers  may  be 
spiked  the  flat  iron,  or  if  desired,  "  T ''  rail.  The  scantling  should  not 
be  spiked  to  the  cross-ties,  as  nails  are  quickly  corroded  by  the  mineral 
vapors  and  waters  of  mines. 


—  13 


DRAINAGE. 


I 


Provision  for  drainage  should  always  be  made  at  the  very  commence- 
ment of  opening  a  mine,  for,  though  the  tunnel  may  be  dry  at  its  mouth, 
when  it  has  been  driven  a  long  way  into  the  mountain  more  or  less  water 
is  nearly  always  encountered.  A  drain  or  trench  should  always  be  cut 
in  the  center  or  at  the  sides  of  every  tunnel  or  drift.  Illy  drained  work- 
ings cause  the  timbers  to  rot  quickly,  and  also  endanger  the  health  of 
the  miners.  Neglect  to  provide  drainage  very  often  results  in  the  neces- 
sity of  retimbering,  which  expense  might  otherwise  have  been  avoided 
for  a  long  time. 

Prospectors,  in  their  haste  to  advance  work  as  speedily  and  as  cheaply 
as  possible,  frequently  fail  to  timber  properly  and  to  provide  for  drainage, 
with  disastrous  results  in  the  future.  Many  months  of  laborious  toil  are 
too  often  lost  in  this  way,  to  say  nothing  of  the  loss  of  life  and  limb  by 
the  unfortunate  miner  caught  in  a  cave  which  might  have  been  easily 
avoided. 

SWELLING   GROUND. 

One  of  the  greatest  difficulties  with  which  miners  have  to  contend  is 
the  swelling  of  the  rock  masses  into  which  their  excavations  have  pene- 
trated. Often  the  force  or  pressure  against  timbers  caused  by  the  swell- 
ing of  the  ground  is  irresistible.  It  is  a  common  feature  of  many  of  the 
Mother  Lode  mines  in  California,  particularly  in  Tuolumne,  Calaveras, 
and  Amador  Counties.  Swelling  bedrock  is  quite  common  in  the  gravel 
drift  mines  of  California.  All  Comstock  miners  know  what  swelling 
ground  is.  It  is  one  of  the  most  serious  obstacles  with  which  they  have 
to  contend. 

In  a  general  way  it  may  be  said  that  the  only  recourse  is  to  timber  in 
the  most  substantial  manner,  and  then,  by  frequently,  or  as  often  as 
necessary,  cutting  out  a  portion  of  the  heavy  ground  and  relieving  the 
pressure  the  timbers  may  be  kept  in  place  and  the  excavation  kept  open. 
Fig.  14  represents  a  cross-section  of  a  tunnel  where  this  trouble  in  its 
worst  form  was  encountered.  By  setting  timbers  in  the  manner  shown 
in  the  cut,  placing  the  sets  close  together,  and  relieving  the  ground  by 
the  removal  of  the  encroaching  portion  from  time  to  time,  the  trouble  is 
reduced  to  a  minimum.  In  the  Hardenburg  Mine,  Amador  County, 
swelling  ground  has  caused  a  great  deal  of  trouble  lately.  The  900-foot 
level  is  run  in  a  zone  of  crushed  foliated  black  slate,  which,  on  the  foot- 
wall  side  of  the  drift,  when  first  broken,  appears  firm  and  solid,  but  in 
a  few  days  it  commences  to  spawl  off  and  to  noticeably  encroach  upon 
the  drift.  It  continues  to  swell,  displacing  timbers  or  breaking  them, 
and  causing  no  end  of  trouble.  Now  such  places  are  timbered  with  18 
and  20-inch  round  timber  and  somewhat  loosely  lagged.  But  few  days 
pass  before  it  is  necessary  to  take  out  lagging  and  cut  away  the  swelled 
ground. 

In  running  the  main  tunnel  of  the  Hidden  Treasure  Mine  at  Forest 
Hill,  in  Placer  County,  swelling  bedrock  was  encountered.  Mr.  Ross  E. 
Browne,  E.M.,  in  his  article,  "  The  ancient  river  beds  of  the  Forest  Hill 
Divide"  {vide  X  report,  State  Mineralogist  of  California),  says  of  this 
occurrence: 

"  The  pressure  of  the  gravel  is  not  great,  but  the  swelling  bedrock  has 
been  a  source  of  trouble,  driving  the  legs  of  the  timber-set  inward  and 


—  14  — 

crushing  the  cap.  After  many  unsuccessful  attempts  to  overcome  this 
difficulty,  the  legs  were  given  an  increasingly  greater  bottom  spread, 
until  finally  it  was  found  that  they  remained  stationary.  The  swelling 
bedrock  is  removed  from  time  to  time  and  the  track  adjusted.  The 
accompanying  cut  shows  the  form  of  tunnel  timber-set  now  used  in  bad 
swelling  ground.  Sets  are  first  put  in  4  feet  apart,  and  in  the  course 
of  a  few  months  center-sets  are  placed  between  these.  Timber-sets  on 
this  plan  have  now  been  in  place  three  years  (1879),  and  are  still  in 
good  condition.  In  8,500  feet  length  of  tunnel  there  are  about  4,000  sets 
of  timbers.  Two  men  are  kept  constantly  employed  in  easing  and 
repairing  the  sets  and  adjusting  the  track." 

Fig.  14. 


^    ^  LOOSE  '^ORAVEl.y 


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'I  J  SWetUNG  0£D'/?OC/C^f  1^     //ilfl  / 


.  / 

Some  of  the  drift  mines  on  Sugar  Loaf  Mountain,  near  Nevada  City, 
Cal.,  that  were  worked  twenty-five  years  ago,  were  timbered  in  a  very 
peculiar  and  unusual  manner,  owing  to  the  swelling  of  the  bedrock. 
Massive  timbers  had  been  placed  time  and  again,  only  to  be  forced  out 
of  place,  or  broken.  At  last  the  method  here  described  was  introduced 
and  found  to  answer  every  requirement  most  admirably.  It  was  subse- 
quently tried  in  some  of  the  other  mines  of  the  neighborhood  with 
equally  satisfactory  results.  Once  firmly  placed,  the  timbers  were  never  | 
again  renewed,  standing  until  the  mine  was  worked  out. 

The  plan  adopted  was  as  follows:  A  drift  of  the  usual  form  was  run 
and  heavily  timbered,  being  well  lagged  overhead.  The  sets  were 
placed  5  feet  from  center  to  center.  As  the  work  of  excavating  thei 
drift  proceeded,  a  triangular  section  was  cut  out  of  each  side  of  the  drift  | 
between  the  posts  of  the  two  adjoining  sets.  These  two  posts  formed  the 
base  of  a  triangle,  the  apex  being  directly  opposite  the  center  of  the  base. 
At  the  apex  a  post  was  set,  the  center  of  which  was  3  feet  from  the 
center  line  of  the  posts  forming  the  base.  Caps  were  placed  reaching 
from  the  post  at  the  apex  to  each  of  those  of  the  base,  and  lagging 
driven  in  diagonally  from  the  drift.  The  two  sides  of  the  triangular 
section  opposite  the  base  were  lagged,  a  considerable  space  being  left 


METHOD   OF  T/MBrRlNa     SWFLLIMG      GROUND     IN    THE    DRITT  MINES     Of 

•SUQAR     LOAF     MOUiNTAIN,     NEAR 

NEVAQA       CITY,    CAL 


Ft?'-  '4-. A 


between  the  lagging  to  atibrd  an  opportunity  for  the  soft  swelling  ground 
to  force  its  way  through  the  open  spaces,  when  it  is  removed.  These 
triangular  spaces  were  continuous;  that  is,  were  cut  opposite  each  set  of 
the  main  drift.  The  method  involved  considerable  extra  expense  in 
mining  and  timbering,  but  it  was  so  infinitely  superior  to  any  plan  pre- 
viously tried  that  it  was  looked  upon  as  a  success  mechanically  and 
financially.  The  accompanying  sketch  will  make  plain  the  details  of 
this  peculiar  method  which  since  its  use  in  the  mines  on  Sugar  Loaf 
Mountain,  seems  to  have  been  lost  sight  of. 

Drifts  sometimes  require  but  a  few  posts  to  support  particular  rock 
masses  that  threaten  to  fall.  Where  a  post  alone  affords  insufficient 
support,  a  heavy  piece  of  plank  (plate)  is  inserted  between  the  top  of 
the  post  and  the  roof. 

RUNNING   GROUND. 

Tunnels  and  shafts  at  times  must  pass  through  soft,  running  ground. 
Zones  of  rock  of  this  description  are  often  found  lying  between  walls  of 
firmer  rock.  The  occurrence  is  not  infrequent  on  the  Mother  Lode  of 
California  when  the  fissure  is  barren  of  quartz  and  filled  with  a  mass  of 
soft  crushed  foliated  black  slate.  It  is  prominent  in  the  Quaker  City, 
Gwin,  Hardenburg,  Kennedy,  and  many  other  mines  on  the  lode. 
Such  ground  is  nearly  always  wet,  and  the  process  of  sinking  or  drift- 
ing in  it  is  attended  with  expense  and  danger.  In  sinking  through  such 
ground  the  miners  usually  make  an  effort  to  push  the  work  and  pass 
through  it  as  quickly  as  possible.  When  the  ground  is  very  wet  and 
runs  easily  it  is  not  always  the  best  plan  to  "  crowd  "  it.  In  some  cases 
the  difficulties  are  more  easily  overcome,  the  expense  reduced,  and  the 
completion  of  the  task  sooner  accomplished  by  going  slowly,  allowing 
the  ground  to  assume  a  more  normal  condition  by  cutting  out  and 
removing  the  material  falling  into  or  forced  into  the  excavation.  When 
water  is  troublesome  in  ground  of  this  character,  the  better  plan  is  to 
permit  it  to  drain  off.  By  so  doing  the  ground  sometimes  becomes 
firmer,  and,  as  a  consequence,  is  more  easily  handled,  timbers  more 
readily  placed  in  position,  and  the  work  carried  on  more  satisfactorily. 
Another  kind  of  ground  difficult  to  timber  is  found  in  some  much 
altered  rocks  where  talc,  steatite  (soapstone),  and  serpentine,  containing 

i  much  water,  have  to  be  passed  through.  The  ground  often  breaks  well 
and  sometimes  stands  well  for  a  time,  but  it  is  treacherous  and  should 
be  promptly  and  substantially  timbered.  Rocks  of  this  description  are 
abundant  in  the  great  auriferous  belt  of  California,  and  as  miners  there 
well  know,  are  usually  fissured  in  every  direction  and  upon  exposure  to 
the  atmosphere  exhibit  a  tendency  to  break  up  (called  blocky  ground). 

I  Great  angular  blocks  and  "  heads  "  (round  bowlders)  drop  from  the  roof 
and  sides  without  warning.  The  former  are  often  wedge-shaped  and 
slip  out  from  the  fissured  rocks  when  the  ground  had  appeared  firm  and 
solid.  The  heads  are  usually  hard  in  the  center,  while  the  outer  portion 
is  quite  soft,  feeling  greasy  to  the  touch.  In  size  these  masses  range 
from  an  inch  or  two  in  diameter  to  those  which  weigh  tons.  Timber 
must  be  placed  in  ground  like  this  immediately  as  the  work  progresses. 
The  sets  should  not  be  more  than  2^  feet  from  center  to  center,  instead 
of  the  usual  distance,  4  to  5  feet,  whether  it  be  in  shaft  or  tunnel.  Lag- 
ging, when  used,  must  also  be  short. 

When  passing  through  slips  or  fissures,  whether  single  or  in  zones,  in 


—  16  — 

any  kind  of  rock,  extraordinary  precautions  should  be  taken,  as  accident 
is  much  more  likely  to  occur  at  such  points  than  in  solid,  unfissured 
ground.  Rock  in  the  vicinity  of  veins  is  nearly  always  more  dangerous 
than  that  at  a  distance  from  the  vein. 


SHAFTS. 

Working  shafts,  as  well  as  tunnels  and  drifts,  should  be  arranged 
with  a  view  to  securing  their  permanency.  Indeed,  in  consideration  of 
future  possibilities,  even  greater  care  should  be  exercised  in  the  selection 
of  their  location  and  in  deciding  upon  their  size,  while  the  manner  of 
timbering  is  most  important.  Worldng  shafts  should  be  so  equipped  as 
to  remain  open  and  be  in  use  as  long  as  ore  remains  in  the  mine  which 
it  will  pay  to  extract.  As  in  all  other  mine  work,  the  amount  of  timber 
required  depends  largely  on  the  size  of  the  shaft  and  more  particularly 
on  the  character  of  the  rock  through  which  it  passes.  Prospecting  shafts 
are  sometimes  sunk  in  good-standing  ground  to  the  depth  of  several 
hundred  feet  without  other  timber  than  a  few  stulls,  to  which  ladders 
are  secured.  The  few  timbers  thus  placed  often  become  insecure  through 
neglect,  particularly  in  regions  where  there  are  climatic  alternations  of 
wet  and  dry.  When  wet,  the  timbers  and  the  wedges  securing  them, 
swell.  With  the  change  to  dryness  they  shrink  and  are  likely  to  drop 
out.  An  additional  danger  results  when  the  rock  walls  crumble,  and 
men  working  below  are  in  constant  danger  from  falling  rocks  and  tim- 
bers. The  wedges  demand  frequent  attention,  for  they  must  be  kept 
driven  well  in  at  all  times.  On  the  desert  and  in  mines  above  timber 
line,  where  timber  is  expensive,  miners  endeavor  to  get  along  with  as 
little  as  possible  and  are  not  very  particular  as  to  the  kind  and  quality 
of  that  which  is  used.  It  would  perhaps  be  a  better  plan  to  dispense 
with  timber  altogether  than  to  place  too  much  dependence  on  sticks  that 
are  likely  to  drop  out  of  position  unexpectedly.  As  a  matter  of  fact, 
the  writer  has  seen  shafts  in  the  Mojave  Desert  mines  more  than  200 
feet  in  depth  without  a  single  stick  of  timber.  The  necessities  of  the 
case  in  sparsely  timbered  regions  and  on  the  desert  have  obliged  the 
miner  to  resort  to  many  novel  plans  to  protect  himself  against  danger 
at  the  least  possible  expense.  He  puts  in  as  substantial  a  frame  of 
timbers  as  he  can  obtain,  or  as  he  may  think  he  can  afford,  using  a  few 
frail  saplings,  thin,  split  lagging,  or  even  brush,  to  support  the  sides  of 
his  shaft.  Fortunately  for  him,  in  the  desert  regions,  where  scarcity  of 
timber  forces  upon  him  this  economical ''  system  "  of  timbering,  the  rock, 
being  nearly  always  dry,  stands  fairly  well,  as  a  rule,  and  expensive 
timbering  is  not  necessary. 

The  extremities  to  which  prospectors  are  often  reduced  to  procure 
timber  in  these  timberless  regions  has  resulted  in  the  adoption  of  a 
method  peculiar  to  such  districts.  While  the  result  is  not  particularly 
pleasing  from  a  workmanlike  standpoint,  it  nevertheless  exemplifies  most 
faithfully  those  principles  which  are  the  foundation  of  the  most  elabo- 
rate system  of  timbering.  In  these  shafts  all  timbers  are  stulls,  each  one 
being  placed  to  support  some  particular  rock  or  mass  which  seemingly 
threatens  to  fall.  Each  stick  is  independent  of  the  others;  there  are  no 
superfluous  timbers,  and  no  attempt  at  system  or  regularity.    As  a  result 


—  17  — 

these  sticks  cross  the  shaft  at  many  angles.  Some  are  horizontal,  but 
most  of  them  inclined  somewhat  from  that  position.  It  sometimes  gives 
the  shaft  timbers  a  spiral  appearance  as  viewed  from  above.  Despite 
the  fact  that  these  timbers  are  placed  so  much  at  variance  with  recog- 
nized methods,  if  placed  at  the  time  of  making  the  excavation,  or  shortly 
thereafter,  and  are  properly  and  firmly  wedged,  they  usually  render  the 
shaft  fairly  safe.  In  that  region  old  redwood  railroad  ties  are  very  fre- 
quently used  for  mine  timbers,  and  answer  admirably,  even  though 
unsuited  for  such  use  from  having  lain  for  months  in  a  railroad  bed, 
being  split  and  often  cut  by  the  rails.  The  miners  are  glad  to  get  them, 
poor  as  the  timber  is,  for  when  once  properly  placed  they  have  been  found 
to  do  very  well,  where  the  pressure  js  not  too  great. 

Shafts  having  a  single  compartment,  such  as  are  frequently  seen  in 
small  mines,  are  timbered  in  a  simple  manner.  The  timbers  consist  of 
two  wall  and  two  end  plates  and  four  posts  to  each  set.  The  method 
shown  in  Fig.  14  C  is  quite  common  and  suited  to  shafts  of  moderate  size 
(5x7  in  the  clear),  having  a  single  compartment.  The  four  frame  timbers 
are  placed  in  position  and  tightly  wedged,  the  posts  being  driven  in  at 
the  corners.  Care  must  be  taken  to  keep  the  sets  in  line.  Sets  are 
ordinarily  5  feet  apart  from  center  to  center.  When  the  ground  is  heavy, 
sets  may  be  placed  closer  than  5  feet.  They  are  often  only  half  that 
distance  from  center  to  center. 

Lagging,  either  split  or  sawed  (2-inch  plank),  is  driven  in  behind 
the  timbers.  It  is  driven  one  half  to  three  quarters  of  the  way  down, 
when  the  lower  ends  of  the  next  set  below  are  inserted  between  the 
timber  and  the  wall.  Later  the  lagging  of  the  set  above  is  driven 
down  to  its  proper  place. 

CRIBBED    SHAFT. 

When  the  pressure  of  the  ground  is  very  heavy  a  crib  of  timbers  is 
built,  the  timbers  being  placed  one  on  another  with  only  a  notch  at  the 
ends  to  hold  them  in  place.  In  soft  ground  it  may  be  necessary  to  use 
lagging,  even  in  a  cribbed  shaft.  All  open  spaces  between  the  walls  and 
the  crib  or  lagging  should  be  filled  with  broken  rock  to  secure  firmness, 
and  to  counteract  any  tendency  of  the  timbers  to  shift.  The  manner  of 
framing  crib  timbers  is  shown  in  the  cut  on  page  18. 


2c 


—  18  — 


Fig. 14  B. 


REACHERS   IN    SHAFTS. 


When  sinking  can  be  carried  on  somewhat  in  advance  of  timbering,  it 
is  sometimes  the  custom,  in  firm  ground,  to  place  long  timbers,  called 
"  reachers,"  across  the  shaft,  the  ends  resting  in  niches  cut  in  the  walls. 
These  having  been  firmly  placed,  the  four  timbers  of  the  set  are  laid 
upon  them  and  firmly  wedged,  and  from  this  foundation  the  sets  are 
built  upward  to  the  next  set  of  reachers  above,  a  distance  of  25  to  30 
feet.  Where  the  shaft  is  sunk  in  country  rock,  or  in  a  large  pillar  of 
ore  (the  latter  to  be  avoided  when  possible),  the  reachers  are  placed 
alternately  in  sets  at  right  angles. 

The  manner  of  framing  the  ends  of  shaft  timbers  where  they  join  at 
the  corners  is  shown  in  the  cuts  of  the  Requa,  Forman,  and  Alma 
shafts  and  the  Argonaut  incline. 

Men  working  in  shafts  placing  timbers  usually  work  suspended  on 
slings  secured  to  timbers  above. 


—  19  — 


fl  — :-]!  -  ^  JLa^ft^...^^.=..^«^^^fe^ht>/WJ.^^tJ^ 


■^Mmmr--^irn^iU"\\  ^^M\mMl  -.^^  I  :,tK>^a.;.4fc  ^^P^#-%J(  3^  W'^^^ir^ 


Fig.  14  C. 


IRON   DOGS   AND   BOLTS. 

In  places  where  the  above  described  methods  of  building  sets  of  shaft 
timbers  on  reachers  is  not  possible,  owing  to  the  soft  nature  of  the  rock 
in  which  the  shaft  is  sunk,  or  where  it  is  desirable  to  run  cages  to  the 
bottom  of  the  mine,  it  was  formerly  the  custom  to  suspend  the  shaft 
timbers  by  ropes  in  a  position  as  near  to  that  desired  as  possible,  and 
to  then  maintain  them  in  that  position  by  driving  iron  dogs  into  the 
timbers,  the  weight  being  supported  by  the  set  next  above,  which  had 
previously  been  secured  by  wedges.  In  some  cases  these  dogs  were  never 
removed.  Many  of  them  may  be  seen  in  the  older  California  mines. 
The  dogs  were  made  of  round  or  square  iron  bars  1x1  inch  or  1x1^ 
inches,  and  having  the  ends  turned  at  right  angles.  The  points  were 
3  or  4  inches  in  length  and  sharp.  The  length  of  the  dog  was  deter- 
mined by  the  distance  from  center  to  center  of  the  sets. 

When  the  rock  was  sufficiently  firm  to  admit  of  the  timbers  being 
firmly  wedged  the  dogs  were  knocked  out.  Iron  dogs  or  bolts  are  useless 
as  a  means  of  support  when  the  surrounding  rock  masses  have  once 
firmly  settled  on  the  timbers. 

A  safer  and  more  convenient  device  has  been  introduced  in  later  years, 
in  the  form  of  iron  bars  having  a  thread  at  one  end  and  a  ring  or  hook 
at  the  other.  These  go  in  pairs,  their  combined  length  exceeding  by  6 
inches  the  distance  from  the  top  of  one  set  to  the  bottom  of  the  next  set 
beneath.  The  manner  of  using  these  hangers  is  as  follows:  A  set  having 
been  securely  wedged  in  its  proper  position,  the  threaded  end  of  the  bolt 
provided  with  a  hook  is  passed  upward  through  a  hole  in  the  plate 
(bored  in  all  timbers  for  the  purpose),  a  washer  passed  over  the  end  of 
the  bolt,  and  a  threaded  nut  screwed  down  onto  it.  A  second  ''  lock- 
nut  "  may  be  used,  but  is  not  necessary.     A  second  similar  bolt  with 


—  20  — 

hook  is  passed  through  a  hole  near  the  opposite  end  of  the  same  timber, 
and  also  secured  with  washer  and  nut.  The  timber  to  be  placed  directly 
below  is  suspended  by  ropes  in  a  position  approximating  that  desired 
and  a  bolt  having  a  ring  at  one  end  is  passed  downward  through  this 
timber,  immediately  below  that  in  the  timber  above,  and  a  similar  bolt 
is  passed  through  the  opposite  end.  Washers  and  nuts  are  placed  on 
the*  ends  of  these  bolts  and  the  rings  are  caught  in  the  hooks  of  the  bolts 
above.  The  nuts  may  now  be  turned  and  the  timber  drawn  to  exactly 
the  position  required,  when  the  ropes  may  be  removed.  All  four  of  the 
timbers  of  this  set  having  been  placed  in  position,  and  being  suspended 
on  the  hangers,  the  posts  are  slipped  in,  the  nuts  tightened  still  further, 
and  the  whole  firmly  wedged,  when  the  next  set  below  may  be  put  in  in 
like  manner.  The  hangers  are  left  a  few  days  or  weeks,  and  in  some 
instances  permanently,  but,  as  previously  stated,  they  are  useless  as  a 
means  of  support  when  the  weight  of  the  surrounding  rock  has  settled 
on  the  timbers. 

Where,  owing  to  the  soft  nature  of  the  ground,  it  is  thought  desirable 
to  have  the  hangers  remain  in  place  indefinitely,  a  bar  having  a  thread 
at  one  end  and  simply  turned  at  a  right  angle  at  the  other,  or  having  a 
solid  hammered  head  with  a  washer,  may  be  used,  being  passed  upward 
through  the  bottom  timber  and  then  through  that  above,  where  the 
adjustment  is  made  by  means  of  a  washer  and  nut;  but  as  these  bars 
are  longer  than  the  distance  between  sets,  their  removal  is  impossible, 
a  set  below  once  having  been  put  in  place.  There  is  no  question  as  to 
the  superiority  of  the  bolts  having  rings  and  hooks  for  either  temporary 
or  permanent  use. 

RETIMBERING    SHAFTS. 

It  very  frequently  occurs  that  shaft  timbers  have  to  be  removed  and 
new  ones  inserted,  and  also  often  necessary  to  reinforce  timbers  already 
in  place.  This  work  frequently  necessitates  the  suspension  of  hoisting 
through  the  shaft.  The  Superintendent  of  the  Wildman  Mine,  at  Sutter 
Creek,  Amador  County,  California,  having  occasion  to  retimber  the  shaft 
between  the  500  and  600  levels  of  the  mine,  constructed  a  chute  1  foot 
square  of  2-inch  plank  in  one  corner  of  a  compartment  of  the  shaft 
reaching  between  these  levels.  It  was  built  in  short  sections,  each  the 
length  of  a  set  of  timbers.  The  work  of  retimbering  was  commenced 
above  and  carried  downward,  all  of  the  refuse  rock,  timber,  etc.,  being 
dumped  into  the  chute.  This  material  was  taken  up  on  the  600  level, 
dumped  into  a  skip  from  time  to  time,  and  sent  to  the  surface;  by  this 
means  the  work  was  quickly  and  safely  carried  on,  sections  of  the  chute 
being  removed  to  keep  pace  with  the  work.  By  means  of  this  device 
there  was  very  little  delay  in  operating  the  skips,  and  hoisting  of  ore 
was  continued  almost  without  interruption  during  the  retimbering  of 
that  portion  of  the  shaft. 

SHAFTS   HAVING   TWO   OR   MORE   COMPARTMENTS. 

Lafge  shafts  are  separated  into  two  or  more  compartments  by  placing 
timbers  called  "  dividers  "  at  intermediate  points  between  the  end  plates. 
They  reach  from  the  wall  plate  on  one  side  to  that  on  the  opposite  side 
of  the  shaft.  These  dividers  are  framed  with  a  short  beveled  tenon, 
broader  at  the  top  than  at  the  bottom.     (See  cuts  of  Forman,  Requa, 


—  21  — 


lER      or      rRAMIN  &      DIVIDER 


and  Alma  shafts.)  These  tenons  fit  exactly  into  mortices  or  notches  in 
the  wall  plates.  At  each  of  the  four  corners  of  the  shaft  and  between 
the  wall  plates,  opposite  each  divider,  is  placed  a  post,  which  is  set  in  a 
shallow  notch  or  seat  cut  in  the  plates.  In  size  the  posts  may  equal 
that  of  the  plates,  or  if  desired  they  may  be  of  smaller  dimensions.  The 
dividers  are  made  the  same  depth  as  the  wall  plates,  but  are  usually 
narrower  across  the  upper  face. 

The  dividers  separating  shafts  into  two  or  more  compartments  may  be 
made  most  secure  by  permitting  the  upper  portion  of  the  beveled  tenon 
to  extend  into  the  wall  plate  2  or  3  inches,  the  bottom  portion  being  let 
in  but  1  inch.  The  post  setting  directly  on  the  divider  holds  it  much 
more  firmly,  and  the  danger  of  having  the  dividers  knocked  out  by  shots 
fired  directly  blow  is  greatly  decreased,  if  not  obviated  entirely.  It  not 
infrequently  occurs  when  dividers  are  framed  so  as  to  set  but  1  inch  into 
the  wall  plates  a  heavy  blast  will  tear  them  out  altogether,  incurring 
expense  of  timber  and  time,  which  may  be  avoided  in  the  manner  stated 
above. 

Drawings  of  two  Comstock  shafts  illustrate  the  manner  of  framing 
and  placing  timbers  in  them.  One  of  these  is  called  an  "  L"  shaft,  and 
was  sunk  by  the  Overman  and  Caledonia  companies  jointly.  It  is 
known  as  the  Forman  shaft.  The  other  is  the  Requa  shaft,  sunk  by 
the  Chollar,  Norcross,  and  Savage  companies.  It  is  a  large  rectangular 
shaft  having  four  compartments,  and  is  a  splendid  example  of  its  kind. 
An  illustration  of  the  new  Alma  shaft  at  Jackson,  Amador  County, 
California,  shows  a  different  style  of  framing.  In  fact,  the  manner  of 
framing  and  joining  the  timbers  of  these  three  shafts  is  totally  different. 

In  size,  shaft  timbers  range  from  8x8  to  20x24,  and  even  larger  dimen- 
sions are  sometimes  employed  in  very  heavy  ground,  particularly  in 
inclined  shafts.  The  wall  plates  are  usually  broader  on  one  side  than 
on  the  other,  and  are  placed  in  position  with  broad  side  up.  End  plates 
are  usually  the  square  of  the  smaller  dimension  of  the  wall  plate. 

Pumping  and  manway  compartments  do  not  require  lining,  but  hoist- 
ing compartments,  particularly  where  cages  are  run,  should  be  lined 
throughout  to  prevent  accident  to  men  who  sometimes  overcrowd  a  cage. 


EDGE    OF   WALL  PLATE   W.  FACING    INSIDE  OF    SHAFT 


'ORMAN  SHAFT  OF  THE  OVERMAN  ANO  CALEDONIA 
3r  SILVER  MIMNG  COMPANIES  COMSTOCK  LODE 


VIRGINIA  CITY  NEVADA 
SCALE     A     INCH    TO  1   FOOT. 


Fig.  10. 


EDGE  OF  END  PLATE  INStOEOF  SHAFT 


Fig.  15  A. 


—  24  — 

There  appears  to  be  less  danger  of  this  where  buckets  or  skips  are  used. 
Every  shaft  in  a  mine  should  be  provided  with  ladder  ways  as  a  means 
of  exit  in  case  of  accident  to  shaft  or  hoisting  machinery. 

Sinking  large  shafts  in  swelling  ground,  in  loose,  watery,  running 
ground,  or  in  quicksand  greatly  multiplies  the  difficulties  and  dangers 
of  the  miner.  There  are  instances  where  shafts  have  been  abandoned 
owing  to  insurmountable  obstacles  which  a  combination  of  engineering 
skill,  capital,  and  labor  were  unable  to  overcome,  but  such  instances  are 
of  rare  occurrence.  Few  shafts  present  greater  difficulties  than  were 
encountered  at  Leadville,  Colorado;  in  the  Lake  Superior  region;  in  some 
coal  mines;  on  the  Comstock,  and  in  Calaveras  and  Amador  Counties, 
California  (the  latter  are  mostly  inclines),  and  some  of  the  shafts  in  the 
regions  mentioned  are  to-day  splendid  and  substantial  monuments  to 
American  engineering  and  to  the  enterprise  of  the  companies  owning 
them. 

The  shaft  of  El  Capitan  Mine,  Nevada  County,  now  the  property  of 
the  Providence  Mining  Company,  was  sunk  through  decomposed  slate 
and  altered  dyke  rock  under  the  most  trying  and  dangerous  conditions. 
After  several  failures,  the  shaft  was  carried  down  to  solid  ground  under 
the  direction  of  Francis  Burns,  who  worked  slowly  and  carefully,  giving 
the  soft  running  ground  time  to  drain.  The  water  being  pumped  from 
the  sump,  after  standing  for  a  time,  appeared  to  drain  the  ground,  and 
it  was  found  that  by  this  means  progress  was  much  more  rapid  than 
when  the  work  was  hurried.  "  Breast-boards  "  were  carried  down  until 
the  dangerous  places  had  been  safely  passed. 

It  is  sometimes  necessary  in  sinking  large  shafts  to  carry  them  down 
in  sections  by  driving  lagging  or  planks  down  in  advance  of  the  exca- 
vation. This  is  known  as  ''  fore-poling.'^  The  section  is  started  at  one 
end  of  the  main  opening  and  advanced  several  feet,  the  lagging  being 
well  braced.  Considerable  water  will  drain  into  this  depression,  making 
the  removal  of  the  ground  from  the  remainder  of  the  shaft  much  easier. 
By  carrying  one  side  of  the  shaft  somewhat  in  advance  of  the  remainder, 
in  this  manner,  loose,  wet  ground  can  be  worked  more  quickly  and  at 
less  expense  than  when  it  is  attempted  to  carry  down  the  entire  shaft  at 
once. 

SPLICED   WALL    PLATES. 

In  cases  where  sinking  cannot  be  carried  on  in  shafts  much  in 
advance  of  timbering  the  wall  plates  may  be  spliced.  The  better  plan 
is  to  extend  the  plate  from  one  side  entirely  across  the  two  hoisting 
compartments,  that  portion  in  the  pumping  compartment  being  in  a 
single  piece,  and  joining  the  longer  piece  directly  opposite  the  divider 
next  to  the  pumping  compartment.  These  joining  ends  of  the  two 
sections  of  wall  plate  should  be  framed  so  as  to  permit  the  divider  to 
lap  over  their  entire  width,  the  upper  half  of  the  plate  sections  being 
removed  so  as  to  admit  the  upper  half  of  the  divider,  as  shown  in  the 
illustration. 

The  post  standing  immediately  upon  the  divider,  and  covering  the 
entire  splice  and  overlap,  prevents  the  divider  from  being  blown  out  by 
heavy  shots  below.  This  plan  also  greatly  facilitates  the  placing  of 
shaft  timbers,  as  there  is  not  that  great  loss  of  time  in  getting  the  wall 
plates  in  position,  which  results  when  long  timbers  are  handled.  There 
is  always  difficulty  and  loss  of  time  where  the  shaft  cannot  be  carried 


25  — 


' -jj^^^^^ATp^-*2 ^=-\    '     T;rq^.,  .,"~n —  .  _-^  i   WAtJF-;  PjyrrrL-  :-.^_____=^ 


rn/NMiNC     POR      SPLICED     WALL   Plate:    and    ovcrlapp.inc    divider. 
FOR     SHArrs. 

down  in  advance  of  the  timbers  far  enough  to  give  room  to  turn  the 
long  wall  plates.  This  system  also  permits  of  the  renewal  of  wall 
plates  and  other  shaft  timbers  by  the  ease  with  which  they  may  all  be 
removed. 

BREAST   BOARDS. 

When  the  ground  has  a  tendency  to  thrust  itself  up  in  the  bottom  of 
the  shaft,  the  plan  of  planking  and  bracing  the  ground  is  sometimes 
resorted  to.  (The  same  principle  is  applied  in  drifting,  when  the  method 
is  referred  to  as  "carrying  breast  boards.")  In  this  method  lagging  is 
driven  down  in  advance  of  the  sinking,  being  supported  in  position 
above  by  a  frame  of  timbers,  either  permanent  or  temporary.  Planks 
are  laid  on  the  bottom  of  the  shaft,  being  secured  by  upright  posts,  which 
abut  against  strong  stulls  or  cross-pieces  firmly  wedged  above.  When 
the  pressure  from  below  begins  to  exert  itself,  a  board  near  the  center  is 
removed  and  the  soft,  pulpy  mass  allowed  to  force  itself  upward.  The 
material  is  removed  until  the  ground  is  eased  somewhat,  when  a  second 
board  is  removed,  the  first  being  replaced  somewhat  lower  than  before, 
and  again  secured;  the  material  coming  up  through  this  new  space  is 
removed  as  in  the  first  instance,  and  in  this  manner  work  proceeds 
entirely  across  the  excavation.  The  process  is  slow  and  requires  consid- 
erable timber,  but  it  is  a  plan  which  may  prove  successful  when  all 
others  fail. 

The  method  of  driving  lagging  in  shafts  is  similar  to  that  explained 
under  the  head  of  drifts.     (See  Fig.  12.) 


—  26  — 

In  some  instances  iron  caissons  have  been  sunk  outside  or  inside  the 
timbers  to  enable  miners  to  pass  through  very  loose,  watery  ground  and 
quicksand.  Where  this  is  not  absolutely  necessary,  wet  places  have 
been  passed  through  by  making  a  clay  lining  between  two  layers  of  close 
planking.  It  may  be  from  2  inches  to  1  foot  in  thickness,  according  to 
the  requirements.  It  has  been  successfully  employed  in  passing  through 
quicksand  and  watery,  loose  ground. 

In  very  bad  wet  ground  the  idea  is  to  form  a  caisson-like  structure 
with  lagging,  the  interior  being  sustained,  as  explained  above,  by  massive 
timbers,  so  placed  as  to  resist  the  pressure  of  the  surrounding  rock  mass. 
The  exigencies  of  each  particular  case  must  determine  the  course  to  be 
pursued. 

The  expedient  of  freezing  soft,  wet,  running  ground,  quicksand,  etc.,  is 
now  much  resorted  to  with  great  success.  It  is  a  patented  process,  but 
finds  general  use  where  applicable. 

Circular  shafts  are  seldom  sunk  in  America  now,  though  very  common 
in  the  early  days  in  California.  There  are  circular  shafts  all  through 
the  old  river-bed  region,  which  pass  down  through  the  tufa  capping  with- 
out a  single  stick  of  timber  from  top  to  bottom.  Many  of  them  are  over 
250  feet  in  depth,  and,  notwithstanding  they  were  made  more  than  forty 
years  ago,  are  still  in  good  condition  and  likely  to  remain  so  for  a  cent- 
ury. The  rectangular  shaft  is  the  most  common  form  in  this  country. 
"  L"  shafts  do  not  find  much  favor  and  have  nothing  to  recommend  them. 
The  size  and  number  of  compartments  of  a  shaft  must  be  determined  by 
the  amount  of  hoisting  expected  to  be  done  through  it. 

STATIONS. 

The  accompanying  sketch  shows  the  manner  of  placing  timbers  at  a 
station  in  an  inclined  shaft.  The  method  in  perpendicular  shafts  is 
essentially  the  same.  The  chain  blocks  are  for  the  purpose  of  landing 
timbers  sent  down  in  the  skip. 

JOINING   OF   GUIDES   IN    SHAFTS. 

Guides  in  shafts  where  cages  are  used  or  where  skips  run  on  guides 
should  be  so  joined  that  there  is  no  likelihood  of  their  warping  and  pro- 
jecting beyond  their  plane,  and  jam  the  cage,  or  skip,  which  is  a  most  dan- 
gerous thing  and  a  great  strain  on  the  cable.  The  overlapping  of  the  ends 
has  been  for  years  a  common  practice;  the  two  ends  being  secured  at  the 
overlap  by  a  single  lag  bolt.  An  improvement  has  been  made  on  this 
plan,  with  a  view  to  greater  safety,  by  joining  the  adjacent  ends  of  sec- 
tions with  a  simple  tongue  and  groove,  like  ordinary  flooring  or  wains- 
coting. ,  The  ends  each  have  a  lag  bolt,  which  makes  them  doubly  secure. 
The  drawings  show  both  styles  for  framing  guides.  Spikes  or  nails 
should  never  be  used,  as  it  requires  much  more  time  to  remove  a  section 
when  repairs  are  necessary.  Guides  are  most  easily  repaired  by  laying 
a  secure  platform  in  the  compartment  at  the  point  requiring  repairs,  the 
men  working  upward  from  set  to  set.  Should  the  whole  shaft,  or  any 
large  portion  of  it,  require  new  guides  at  any  time,  the  platform  should 
be  put  in  as  described.  The  hood  is  removed  from  the  cage  and  a  bottom 
of  loose  boards  laid  on  the  floor.  The  workmen  at  the  platform  unscrew 
the  lag  bolts  and  take  out  the  old,  worn  guides.     The  cage  being  lowered 


I     1 


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QU»DE 


MANNER      OF     FRAMlfx/G      AND 
SECURING      GU/DETS. 


p 


FJQ   fS.D. 


—  27  — 
1 

to  the  proper  point,  the  old  guides  are  passejd  up  through  a  hole  made 
in  the  bottom  of  the  cage,  and  the  new  guides  passed  down  in  the  same 
manner  and  put  in  place.  In  this  way  the  guides  may  be  removed  for 
a  thousand  feet  in  a  single  day  by  a  gang  of  good  workmen.  Other 
repairs  in  the  shaft  may  be  made  in  a  somewhat  similar  manner. 

INCLINES. 

Inclined  shafts  are  somewhat  different  from  those  that  are  vertical, 
and  are  probably  quite  as  numerous.  In  California  the  number  of 
inclined  shafts  far  exceeds  those  that  are  vertical,  being,  as  a  rule,  sunk 
on  the  vein,  which,  in  a  majority  of  cases,  dips  at  some  angle  from  the 
horizontal.  In  a  general  way  what  has  been  said  of  vertical  shafts 
applies  to  those  that  are  inclined.  There  is  considerable  dilference,  how- 
ever, in  the  manner  of  framing  timbers  for  an  incline,  and  while  timbers 
framed  for  an  incline  will  do,  perhaps,  equally  well  in  a  vertical  shaft, 
those  framed  as  already  shown  in  the  illustration  are  not  preferred  in  an 
incline.  An  illustration  of  the  method  of  framing  timbers  for  the  new 
Argonaut  shaft  at  Jackson,  Amador  County,  California,  which  is  expected 
to  reach  a  depth  of  2,000  feet  on  the  incline  (63°),  is  given.  It  resembles 
somewhat  the  new  Alma  shaft,  also  at  Jackson,  though  the  first  400  or 
600  feet  of  the  Alma  will  be  vertical. 

STOPES   AND    CHAMBERS. 

The  cuttings  in  mines  which  require  the  most  care  and  greatest  skill 
in  placing  timbers  to  support  overhanging  ground  are  "  stopes "  and 
large  "  chambers."  The  method  adopted  must  always  depend  upon  the 
size  of  the  excavation,  character  of  the  ore  and  of  the  walls,  the  pitch 
of  the  vein  or  ore  shoot,  and  also  on  the  expense  of  the  timber. 

TAKING   ANGLES   AND    DISTANCE   BETWEEN   WALLS. 

A  very  convenient  instrument  for  measuring  the  distance  between  the 
hanging  and  foot  walls  of  the  vein,  and  to  determine  their  respective 
angles  of  inclination,  for  the  purpose  of  cutting  stulls  with  proper  length 
and  bevels,  is  shown  in  the  accompanying  illustration.  It  consists  of 
two  flat  planed  boards  having  slots,  as  shown  in  the  drawing,  and  fitted 
with  thumb  screws,  s  s  s.  At  either  end  is  a  movable  arm,  A  A.  These 
are  placed  against  the  walls  and  the  screws  tightened,  the  distance 
between  walls  being  ascertained  by  lengthening  or  shortening  the  instru- 
ment by  means  of  the  sliding  arrangement.  Having  carefully  taken  the 
required  measurements,  there  can  be  no  mistake  as  to  the  kind  of  stull 
required. 

TIMBERING   A    SOFT    HANGING   WALL. 

In  some  portions  of  the  New  Almaden  Quicksilver  Mine,  where  the 
width  of  ore  stoped  is  about  10  feet,  an  unusual  method  of  timbering 
has  been  adopted.  The  foot  wall  is  usually  hard  and  solid,  while  the 
"  alta,"  as  the  hanging  wall  is  called,  is  almost  always  soft  and  shelly, 
and  is  considered  dangerous  ground.  Heavy  stulls  are  placed  at  regu- 
lar distances  (about  8  feet),  and  are  set  in  line  one  above  another.    Im- 


—  28 


»^>^^;;''" 


/ 


^  METH  00       or 
TIM^eRING      SMALL 
STORES 

IN    THC 

NEW    ALMADEN 

QUICKSILVER     MINC. 


¥-MMu^^- 


'^n$'Mij:n^r. 


y. 


mediately  above  the  stull  a  second  shorter  timber  is  laid,  which  rests 
upon  the  foot  wall  and  reaches  within  about  a  foot  of  the  hanging  wall. 
A  plate  or  cap  is  inserted  over  the  upper  end  of  this  auxiliary  stull, 
which  reaches  horizontally  across  to  the  next  stulls,  which  are  similarly 
placed.  Heavy  lagging  is  driven  upward  along  the  hanging  wall,  the 
lower  ends  of  which  rest  upon  the  cap  and  the  upper  ends  upon  the  lower 
ends  of  the  lagging  of  the  next  set  above.  The  two  stulls  are  bolted 
together  near  the  top  and  bottom  for  additional  strength  and  security. 
Redwood  has  been  used  quite  extensively  in  timbering  this  mine,  and  it 
is  claimed  it  has  given  satisfaction.  The  accompanying  sketch  will  show 
this  method  of  timbering.  The  large  stopes  of  the  New  Almaden  are 
timbered  in  square  sets. 

FLAT   OR   BLANKET   VEINS. 

In  veins  which  lie  quite  flat,  the  thickness  of  the  vein  and  the  system 
of  mining  must  determine  the  character  of  timbering  to  a  great  extent, 
as  well  as  the  character  of  the  walls.     Where  the  vein  is  thin  (a  foot  or 


—  29  — 

two)  very  little  timber  is  required,  the  waste  rock  filling  the  entire  spac8 
behind  the  miner.  Where  the  mineral  deposit  is  thicker  and  timber  is 
necessary  various  methods  are  pursued.  Some  ground  stands  well  by 
simply  leaving  pillars  of  mineral.  In  other  cases  a  series  of  upright 
posts  and  breasting  caps  will  sustain  the  roof,  the  posts  being  placed  in 
rows  directly  back  of  the  workmen  and  as  close  to  the  face  as  the  neces- 
sity demands.  The  foot  of  the  post  rests  either  directly  on  the  rock 
floor  or  upon  a  block  of  wood  or  piece  of  heavy  plank.  The  posts  are 
forced  into  position  by  driving  them  up  with  heavy  hammers.  Care 
must  be  taken  that  these  posts  are  so  placed  as  to  receive  the  weight  of 
the  roof  directly  and  not  at  an  angle.  These  timbers  are  set  in  lines 
standing  in  two,  three,  or  four  rows  back  from  the  face,  the  waste  being 
piled  behind  as  the  work  advances.  In  this  manner,  by  exercising  care, 
many  sticks  can  be  recovered  before  the  weight  settles  so  heavily  on  the 
refuse  rock  as  to  render  it  impossible  to  remove  the  timbers.  Some  fiat 
veins  make  little  or  no  waste.  It  is  then  necessary  to  follow  the  "  pillar 
and  stall "  system  of  extraction,  considerable  blocks  being  left  to  sustain 
the  roof.  Posts  and  caps  are  used  in  this  system  also.  Frequently  the 
caps  reach  in  a  continuous  line  from  post  to  post,  joining  the  next  set, 
the  ends  of  two  caps  resting  on  a  single  post,  the  combined  sets  being  a 
hundred  feet  or  more  in  width.  Large  timbers  thus  placed  will  support 
great  weight,  but  if  small  rocks  fall  from  the  roof  lagging  must  also  be 
employed.     This  system  is  much  in  use  in  California  gravel  drift  mines. 

When  a  vein  lying  nearly,  or  quite  horizontal,  and  making  no  waste, 
is  to  be  mined,  a  drift  should  be  run  along  the  lowest  portion  of  the 
deposit,  this  point  having  been  reached  by  incline  or  shaft.  The  work 
advances  toward  the  surface,  good  sized  pillars  being  left  to  sustain  the 
roof.  If  timber  is  necessary,  it  is  put  in  place  in  the  manner  required. 
The  work  having  advanced  sufficiently  far  toward  the  surface,  the  pillars 
may  now  be  cut  out  at  the  back  end,  while  the  work  progresses  as  before. 
As  the  pillars  are  removed  more  timber  must  be  put  in,  or  waste  from 
the  surface  must  be  piled  in  cribs  of  timber  built  in  the  workings  already 
made.  Usually  some  timber  can  be  recovered  in  this  way  and  the 
caving  of  the  roof  after  the  complete  removal  of  the  ore,  or  mineral,  does 
no  harm.  The  main  gangways  should  be  substantially  timbered,  if 
necessary,  as  it  is  desirable  to  keep  it  open  to  the  lowest  working  level 
at  all  times. 

The  ''long  wall"  system  of  extracting  ore  is  usually  carried  from  the 
surface  inward,  a  main  gangway  having  been  first  driven  ahead  to  a  con- 
nection with  a  ventilating  shaft,  when  possible.  All  the  ore  is  removed 
at  once,  the  waste  being  thrown  back  of  the  miners,  who  carry  the  breast 
forward  with  the  center  considerably  in  advance  of  the  sides,  the  excava- 
tion being  in  form  somewhat  like  the  letter  "A,"  with  the  apex  forward. 
The  waste  is  thrown  into  the  center  to  support  the  roof,  while  the  side 
passages  permit  of  a  free  circulation  of  air  all  along  the  face. 

STEEPLY   INCLINED   VEINS. 

In  vertical  or  steeply  inclined  veins,  the  principles  governing  the 
methods  of  timbering  are  essentially  the  same  as  those  above  explained, 
though  the  application  is  different.  In  such  workings  the  post  of  the 
flat  vein  becomes  a  "  stull." 


—  30  — 


OVERHAND    STOPING. 


When  a  working  drift  is  driven  along  a  vein  in  ore  and  it  is  the 
intention  to  "stope"  out  the  ore,  the  character  of  the  walls  and  the 
width  of  the  vein  or  deposit  must  determine  the  method  of  timbering. 
If  the  walls  be  hard  and  firm,  and  the  vein  not  more  than  10  or  12  feet 


wide,  posts  are  not  absolutely  necessary.  Stulls  of  the  proper  length  are 
placed  with  the  lower  end  resting  on  the  foot  wall,  or  in  a  niche  cut  for 
the  purpose,  the  upper  end  being  placed  against  the  hanging  wall  and 
driven  downward  until  it  stands  at  a  few  degrees  above  a  right  angle 
with  that  wall.     (See   Figs.  16  and   18.)     When  the  foot  wall  has  a 

greater  inclination  than  the  hanging 
wall,  a  support  resting  on  the  floor 
of  the  drift  must  be  placed  under 
the  lower  end  of  the  stull.  Should 
the  foot  wall  have  a  less  inclination 
than  the  hanging  wall,  the  foot  of  the 
stull  may  be  secured  by  driving  in 
stout  wedges  from  the  upper  side. 
Where  the  foot  wall  is  sufhciently 
hard  and  firm,  a  niche  in  either  case; 
will  answer  as  a  secure  rest  for  the: 
lower  end  of  the  stull.  Where  the 
vein  is  more  than  10  feet  in  width 
and  additional  support  appears  nec- 
essary, resort  may  be  had  to  the  plans 
shown  in  Figs.  19  to  29. 
In  case  either  wall,  or  both  of  them,  is  too  soft  to  safely  sustain  stulls 
under  the  pressure  of  ore  or  waste  to  be  piled  upon  them,  a  plate  (usually 
a  2  or  3-inch  plank)  is  inserted  behind  the  stull  on  either  wall  or  both, 
as  may  be  necessary.     (Figs.  17  and  25.) 

When  the  walls  are  very  soft,  and  even  with  the  use  of  plates,  render 
timbering  insecure,  the  stulls  may  be  placed  at  right  angles  to  the 
walls,  the  ends  resting  upon  posts.  Mining  upward,  the  posts  of  each 
floor  rest  upon  the  stulls  under  foot  and  immediately  above  the  posts  on 
the  floor  below.  In  this  manner  a  stope  in  soft  walls  may  be  carried  to 
any  desired  height.  (Fig.  24  A.)  In  such  instances  it  is  necessary 
to  place  longitudinal  braces  or  "ties"  reaching  from  cap  to  cap  at 


—  31  — 


—  32  — 


right  angles  to  the  stull.     These  ties  may  be  of  smaller  dimensions  than| 
the  stull  and  post  timbers. 

The  method  shown  in  Fig.  19  may  be  employed  where  the  vein 
exceeds  8  or  10  feet  and  when  sticks  sufficiently  large  to  support  the 
weight  of  ore  or  waste  cannot  be  obtained.  Fig.  20  may  be  employed 
in  the  same  manner  with  a  greater  width  of  vein.  Both  of  these  instances 
presume  considerable  waste  to  result  from  mining,  which  will,  to  a  great 
extent,  fill  the  excavation.     Fig.  23  afibrds  a  firm  support  to  a  stull  in 

a  wide  place  in  the  vein,  and  Fig.  22 
the  same  in  a  still  broader  vertical  vein. 
Fig.  25  shows  how,  in  a  vein  of  low  dip 
and  considerable  width,  a  stull  may  be 
firmly  supported  to  retain  waste  or  ore 
coming  down  from  the  stope  above.] 
In  soft  vein  and  wall  rock  a  substan- 
tial method  of  placing  sill,  stull,  and 
post  is  shown  in  Fig.  26. 

Stulls  are  placed  at  distances  rang- 
ing from  2 1  to  6  feet,  as  may  be 
required.  On  them  are  laid  split 
lagging,  forming  a  floor.  As  the 
miner  stands  on  the  floor  thus  im- 
provised, he  breaks  down  the  ore, 
separating  it  from  the  waste,  if  there 
be  any,  and  sending  the  ore  into  the 
''level"  or  main  passageway  below, 
allowing  the  waste  to  accumulate  on 
the  floor.  The  waste  often  occurs; 
to  such  an  extent  that  a  portion  of; 
it  also  has  to  be  sent  to  the  surface. 
When  this  is  the  case,  very  little 
timber  is  required  in  the  stopes. 
When,  however,  the  quantity  of  waste 
is  small,  it  is  often  necessary  to 
build  a  temporary  staging  upon  which 
to  stand  until  a  sufficient  space  is  cut  out  above  to  admit  of  laying  a 
second  tier  of  stulls  to  sustain  the  floor.  Floors  are  6  to  8  feet  apart 
and  sometimes  even  more. 

A  passageway,  called  a  "mill  hole,"  "chute,"  or  "slide,"  is  left  every 
30  to  50  feet  for  the  purpose  of  sending  ore  to  the  level  below,  as  the 
work  progresses  upward.  The  distance  between  these  slides  is  deter- 
mined by  the  dip  of  the  vein.  They  may  be  a  greater  distance  apart  in 
a  steeply  inclined  vein  than  in  one  having  a  low  angle  of  inclination. 
Rock  will  not  run  freely  on  a  slope  having  a  slope  of  less  than  40  degrees, 
and  more  is  preferable.  In  cases  where  the  slope  angle  is  low,  it  is  a  good 
idea  to  line  the  slide  with  plank  to  facilitate  the  delivery  of  the  ore  to 
the  level  beneath.  In  opening  a  stope  between  levels,  the  best  method 
is  to  make  a  raise  from  level  to  level,  building  a  loading  chute  at  the 
bottom.  Then  at  a  short  distance  to  one  side  (15  or  20  feet)  a  second 
raise  is  carried  up  about  1 5  feet  and  connected  with  the  winze.  From 
this  point  the  stope  is  opened,  the  excavation  being  carried  upward  and  the 
ore  being  passed  down  through  the  winze  to  the  loading  chute.  As  the 
floors  are  carried  up  a  crib  is  built  around  the  winze,  keeping  it  constantly 


—  33  — 


open.  This  plan  secures  economy  of  labor  and  affords  the  best  obtain- 
able ventilation.  The  stoping  of  ore  continues  to  within  a  few  feet  of 
the  level  above,  and  is  then  discontinued  for  the  time  being,  this  mass 
of  ore  and  that  remaining  within  a  few  feet  of  the  floor  beneath  being  left 
to  be  taken  out  the  last  thing  before  abandoning  this  portion  of  the  mine. 
When  ore  is  very  rich  it  is  the  custom  to  blast  or  pick  it  down  upon 
canvas  or  boards,  keeping  it  separate  as  far  as  possible  from  the  waste, 
the  ore  being  sacked  in  the  mine.  The  methods  above  described  apply 
to  overhand  stoping,  that  is,  excavating  from  a  level  upward. 
3c 


—  34  — 

UNDERHAND    STOPING 

Is  the  term  used  to  indicate  an  operation  the  reverse  of  that  just 
described,  being  the  method  by  which  the  miner  takes  out  the  floor  of 
his  level  and  continues  the  excavation  downward  in  a  series  of  steps  7  or 
8  feet  in  height.  In  this  method  it  is  best  for  the  economical  handling 
of  the  ore,  for  ventilation,  and  for  drainage,  to  have  established  a  con- 
nection by  winze  with  the  level  next  below,  or  it  will  be  necessary  to  hoist 
all  the  ore  and  water  from  the  stope  to  the  level  above.  The  waste,  if 
there  be  any,  is  thrown  on  platforms  or  floors  between  the  face  of  each 
floor  and  the  winze,  slide,*  or  chute.  This  method  is  not  advisable 
except  in  narrow,  rich  veins. 

Underhand  stoping  is  not  commonly  followed,  but  may  be  recom- 
mended in  working  small  veins  of  very  rich  ore.  It  requires  usually 
more  timber  than  overhand  stoping  and  the  timber  cannot  be  recov- 
ered as  in  the  latter  method. 

CONNECTING   LEVELS. 

When  stoping  by  the  overhand  system,  on  approaching  the  floor  of 
the  level  above  it  is  necessary,  where  posts  and  caps  have  been  used, 
whether  sills  were  used  or  not,  to  take  some  precaution  to  prevent  the 
falling  out  of  these  timbers  and  the  consequent  caving  of  the  filled  stope 
above,  should  there  be  any.  The  plan  adopted  in  the  Bi-metallic  Mine, 
near  Phillipsburgh,  Montana,  is  the  most  expeditious  and  the  safest. 
When  ready  to  break  through  the  floor  under  any  particular  sill  or  set 
of  timbers,  a  stout  piece  of  timber  (sprag)  is  placed  between  the  posts  a 
few  inches  above  the  floor  (at  A)  and  wedged  in  hard  with  shingle 
wedges.  A  heavy  stick  of  timber  (B  B)  long  enough  to  reach  across 
three  sets  (kept  on  each  level  of  the  mine  for  this  purpose)  is  lifted  to 
the  roof  of  the  gangway,  midway  between  the  posts,  one  end  being  under 
the  cap  which  forms  a  portion  of  the  set  of  which  the  sill  to  be  removed 
is  also  a  part.  This  timber  acts  like  a  lever  having  a  fulcrum  at  C,  in 
the  form  of  a  post  which  supports  it,  the  foot  resting  in  the  center  of  the 
drift  on  the  sill  D.  Wedges  are  driven  in  at  E,  making  it  firm  and 
rigid.  Wedges  are  then  driven  in  at  F  and  at  C,  and  the  rock  beneath 
may  then  safely  be  extracted,  the  timber-set  G  G  being  held  in  position, 
the  superincumbent  weight  being  transferred  to  the  points  D  and  E.  As 
a  matter  of  course,  the  sill  of  the  set  G  G  will  drop  out  when  the  rock 
upon  which  it  has  rested  has  been  removed.  The  remainder  of  the  set 
may  then  be  connected  with  the  timbers  of  the  sets  beneath  in  any 
manner  the  case  requires. 

STRENGTH    OF   TIMBERS. 

In  placing  stulls  to  sustain  the  weight  of  waste,  or  to  store  ore  already 
broken,  the  size  and  number  of  timbers  to  be  employed  must  be  deter- 
mined by  the  width  of  the  vein  and  the  height  to  which  the  waste  or  ore 
is  likely  to  accumulate.  It  is  considered  better  to  increase  the  number 
rather  than  the  size  of  stulls.  With  good  walls,  stulls  7  feet  in  lengtli, 
having  a  thickness  of  1 2  inches,  placed  30  inches  apart,  are  calculated 


♦The  term  "ore  slide  "  appears  preferable  to  the  word  "cliute,"as  conflict  is  thereby 
ayoided  with  the  word  "ore  shoot^'  as  applied  to  a  body  of  ore. 


\ 


RT^ 


— Rf. 


^M 


OEVICC        USED 

I  N       CONNECTIN  Q 

LCVCLff. 


^<\-^ 


./,' 


STO  P  E 


^   .'    .'    ■'  .'.  ■.  'FFR 


CAP 


5PRAG 


SI  LL 


CAR 


SECTION        AT        «•& 


S  J  L  L 

SECTION      AT    H 


—  35  — 


—  36  — 

to  sustain  60  feet  of  waste  or  broken  ore  in  a  vein  standing  at  a  high 
angle.  After  waste  has  remained  in  place  for  some  time  it  settles,  and 
in  some  instances  becomes  so  firm  as  to  retain  its  solidity  after  the 
stulls  have  fallen  out  or  have  been  removed.  This  need  not  be  expected 
in  wide  veins. 

When  it  becomes  necessary  to  quickly  catch  up  settling  stull  timbers 
or  caps,  a  stout  post,  which  will  just  slip  under  the  sinking  timber,  is 
placed  in  position  and  four  stout  wooden  wedges,  having  the  inclined 
planes  sloping  alternately  in  different  directions,  are  driven  in  between 
the  post  and  stull.  This  plan  will  recover  the  subsidence,  if  not  too 
great,  and  permit  of  reinforcing  the  timbers  without  losing  ground. 


THE      SAODLC     WEDGES, 

IN   USE    AX  THC 

BUCHANAN     MINC, 

roOLUMNE    COUHTY,     CAL. 


SADDLE    BACKS. 

A  peculiar  method  of  timbering,  known  as  the  "  saddle,  back,"  is  in 
vogue  in  some  portions  of  Colorado.  It  appears  to  do  well  in  the  lead- 
silver  mines  having  good  limestone  roofs  and  walls.  It  may  be  considered 
a  modification  of  the  "  square-set."  It  requires  less  timber  and  is  far  less 
substantial.  It  will  not  do  in  heavy  ground.  The  details  differ  with 
the  various  conditions  encountered,  but  the.  principles  are  those  obtain- 
ing in  all  other  timber  systems — the  application  of  resistance  to  pressure. 
The  drawings  illustrate  one  method  of  setting  up  the  saddle  back. 

LOADING   CHUTES. 


The  accompanying  sketch  shows  a  design  for  a  loading  chute  or  slide, 
though  they  are  not  always  made  as  elaborate  as  represented  in  the 
drawing.  The  inclination  of  the  bottom  should  exceed  30  degrees,  ores 
that  are  soft  and  wet  requiring  the  slide  to  have  a  greater  pitch  than 
those  that  are  dry.  Between  the  two  upright  posts  which  reach  from 
the  floor  of  the  drift  to  the  roof  or  to  stout  stulls  overhead,  two  short 


—  37  — 


A     LOADING    CHUTE 

Fig.  31. 


uprights  are  placed,  and  on  top  of  them,  reaching  from  one  to  the  other, 
is  laid  a  4x6  scantling.  The  gate,  furnished  with  ratchet  and  wheel  and 
pinion,  may  be  dispensed  with,  loose  boards  being  substituted,  which 
may  be  pried  up,  when  desired,  with  a  bar.  It  is  well  always  to  build 
loading  chutes  in  a  substantial  manner,  so  that  rebuilding  may  not  be 


—  38  — 

necessary.  It  is  a  wise  plan  to  provide  false  sides  and  bottoms,  which 
may  be  quickly  renewed. 

The  posts  supporting  loading  chutes  are  not  alwaj's  placed  perpen- 
dicular. In  steeply  inclined  veins  it  is  sometimes  desirable  to  set  them 
inclining  forward.     In  vertical  veins  they  are  built  across  the  vein. 

In  square  sets,  ore  bins  are  constructed  within  the  sets  and  the  chutes 
are  attached  to  the  caps  or  ties,  being  arranged  at  convenient  distances 
from  each  other. 

In  some  mines,  as  in  the  Golden  Gate,  at  Sonora,  in  Tuolumne  County, 
large  storage  bins  are  constructed  below  the  floors  of  the  levels  at  the 
hoisting  shaft,  provided  with  a  loading  chute.  The  skip  is  stopped  at  the 
proper  point  and  loaded.  In  this  manner  the  necessity  of  waiting  for  cars, 
or  loaded  cars  and  men  waiting  for  the  skip,  is  obviated.  In  this  mine 
loading  chutes  are  provided  on  the  several  levels  from  the  stopes  over- 
head, as  a  matter  of  course  being  constructed  in  the  ordinary  manner. 

GREAT    CHAMBERS   AND    SQUARE   SETS. 

The  systems  of  timbering  hereinbefore  described  refer  particularly  to 
veins  having  a  width  not  exceeding  12  feet,  though  mines  have  been 
worked  under  great  difficulties,  and  where  the  operations  were  attended 
with  extreme  danger,  where  the  distance  between  walls  was  20  and  even 
25  feet.  An  instance  may  be  mentioned  in  California  in  the  Mount 
Jefierson  Mine,  at  Groveland,  in  Tuolumne  County,  where  the  vein  was 
25  feet  from  wall  to  wall.  A  very  ingenious  system  of  timbering  was 
introduced  in  1854,  or  thereabouts,  consisting  of  long  stulls  supported 
by  wall  and  inside  props  7  feet  apart.  Longitudinal  braces,  or  ties,  were 
also  introduced  to  support  the  timbers  longitudinally,  but  the  support 
was  insufficient,  and  a  most  disastrous  case  resulted.  It  is  a  matter  of 
absolute  impossibility,  however,  to  recover,  by  the  methods  thus  far  given, 
all  the  ore  from  such  great  masses  of  mineral  as  were  found  in  the  Com- 
stock  Lode,  where  one  ore  body,  the  Great  Bonanza,  measured  340  feet 
in  width  at  one  point,  600  feet  in  height,  and  1,250  feet  in  length.  Stopes 
in  the  various  mines  of  the  Homestake  group,  in  the  Black  Hills,  South 
Dakota,  range  from  40  to  150  feet  in  width  and  several  hundred  feet  in 
length  and  height.  The  Caledonia  Mine,  of  this  group,  measured  on  the 
300-foot  level  195  feet  horizontally.  The  Homestake  vein  at  the  sur- 
face, in  the  open  cut,  is  360  feet  wide,  by  actual  measurement. 

In  California  there  are  many  mines  of  great  value  that  cannot  be 
worked  by  any  system  of  stulls.  The  Stonewall  Mine,  in  San  Diego 
County,  has  20  feet  or  more  of  vein  in  places.  The  Alvord  Gold 
Mine,  in  San  Bernardino  County,  is  a  very  wide  vein.  The  Odessa, 
Occidental,  Oriental,  Silver  Monument,  and  Waterloo  Mines,  of  the  Calico 
District,  measure  30  to  over  100  feet  in  width.  Some  of  the  mines  of 
Bodie  have  very  broad  veins.  The  Josephine  Mine,  in  Mariposa  County, 
has  an  immense  ore  shoot  50  feet  wide.  The  Utica-Stickles  Mine,  at 
Angels,  Calaveras  County,  is  40  to  over  100  feet  wide,  and  the  Gover  Mine, 
of  Amador,  has  an  ore  body  30  to  50  feet  wide.  The  Zeila,  at  Jackson,  is 
working  an  immense  mass  of  ore.  The  Boston  Mine,  near  Mokelumne 
Hill,  is  40  to  60  feet  wide,  and  some  of  the  ore  bodies  in  the  larger  quick- 
silver mines  are  of  prodigious  size.  In  addition  to  these  there  are  many 
other  mines  on  the  gold  belt  of  California  where  the  great  width  of  vein 


—  39  — 

]n'ecliides  the  extraction  of  the  ore  by  the  use  of  any  system  of  stulls  or 
<imple  posts  and  caps. 

Veins  and  ore  bodies  of  large  size  can  be  safely,  completely,  and 
cheaply  mined  by  using  what  is  known  as  the  "  square  set "  system  of 
timbering,  introduced  in  1860,  by  Philip  Deidesheimer,  while  Superin- 
tendent of  the  Ophir  Mine,  on  the  Comstock  Lode. 

INVENTION    OF   SQUARE   SETS. 

The  following  interesting  reference  to  early  mining  on  the  Comstock 
is  from  Monograph  IV,  of  the  United  States  Geological  Survey,  "Com- 
stock Mining  and  Miners." 

''At  the  50-foot  level  (of  the  Ophir  Mine)  the  vein  of  black  sulphu- 
rets  was  only  8  or  4  feet  thick,  and  could  readily  be  extracted'  through  a 
drift  along  its  line,  propping  up  the  walls  and  roof,  when  necessary,  by 
simple  uprights  and  caps.  As  the  ledge  descended  the  sulphuret  vein 
grew  broader,  until  at  a  depth  of  175  feet  it  was  65  feet  in  width,  and 
the  miners  were  at  a  loss  how  to  proceed,  for  the  ore  was  so  soft  and 
crumbling  that  pillars  could  not  be  left  to  support  the  roof.  They 
spliced  timber  together  to  hold  up  the  caving  ground,  but  these  jointed 
props  were  too  weak  and  illy  supported  to  withstand  the  pressure  upon 
them,  and  were  constantly  broken  and  thrown  out  of  place.  The  dilemma 
was  a  curious  one.  Surrounded  by  riches  they  were  unable  to  carry 
them  off. 

"The  company  was  at  a  loss  what  to  do,  but  finally  secured  the  serv- 
ices of  Philip  Deidesheimer,  of  Georgetown,  California,  who  visited  and 
inspected  the  treasure-lined  stopes  of  the  Ophir." 

That  the  ore  body  could  not  be  extracted  in  the  usual  manner  was  at 
once  apparent,  and  Mr.  Deidesheimer  says  he  set  about  his  task  with 
some  misgivings.  He  did  not  at  one  stride  grasp  the  idea  of  the  square 
set,  but  the  system  which  now  bears  his  name  was  the  outgrowth  of  cir- 
cumstances and  the  very  necessities  of  the  case.  He  instituted  a  policy, 
however,  the  wisdom  of  which  soon  became  apparent. 

The  first  step  was  to  cross-cut  the  vein  from  wall  to  wall,  starting  from 
a  drift  on  the  hanging  wall  side  of  the  vein.  As  the  work  advanced  he 
set  up  posts  and  placed  caps  above  them,  not  across  the  course  of  the 
drift,  as  is  usually  done,  but  along  the  sides,  the  idea  being  to  form, 
when  completed,  a  line  of  caps  which  would  reach  continuously  from 
wall  to  wall.  To  accomplish  this  the  ends  of  two  caps  were  placed  upon 
each  post,  except  at  the  ends.  These  novel  sets  were  held  in  place  by 
pieces  of  2x4  scantling  4^  feet  in  length  and  reaching  across  the  drift 
from  near  the  top  of  a  post  to  that  opposite. 

Having  successfully  driven  the  cross-cut,  Mr.  Deidesheimer  now  ran  a 
drift  some  distance  along  the  foot  wall,  timbering  with  posts  and  caps 
in  the  ordinary  manner;  that  is,  the  caps  were  placed  upon  the  posts 
at  right  angles  to  the  drift  and  parallel  with  those  in  the  cross-cut.  The 
posts  in  each  case  were  set  perpendicular.  Returning  to  the  point  where 
these  operations  were  begun,  a  second  section  by  the  side  of  the  first 
cross-cut  was  taken  out  and  timbered  with  a  single  line  of  posts  and 
caps,  the  2x4  scantling  being  placed  as  in  the  first  case.  When  this  sec- 
tion was  completed  there  were  standing  three  lines  of  posts  surmounted 
by  three  lines  of  caps,  extending  from  the  foot  to  the  hanging  wall. 
This  was  not  really  a  new  idea,  as  Mr.  Deidesheimer  had  previously 


—  40  — 

employed  the  same  method  in  his  drift  mine  on  Forest  Hill,  when  thej 
breast  was  carried  in  125  feet  wide,  the  roof  being  supported  by  rows  of] 
posts  with  continuous  caps. 


—   41 


—  42  — 

The  work  thus  far  performed  in  the  Ophir  revealed  the  fact  that  an 
extremely  rich  body  of  ore  extended  upward  from  the  level  where  this 
work  had  been  done.  The  miners  were  directed  to  commence  stoping 
upward  in  the  body  of  soft,  black,  crumbling  ore,  and  soon  a  consider- 
able excavation  had  been  made.  It  became  evident  that  the  ground 
must  be  secured  at  once. 

In  the  Georgetown  Mine,  that  Mr.  Deidesheimer  had  left  but  a  short 
time  before,  the  vein  was  vertical,  and  the  walls  were  so  soft  and  crumb- 
ling that  in  order  to  stope  out  the  mineral  he  had  resorted  to  the  expe- 
dient of  setting  one  post  directly  above  another,  the  lower  end  resting  on 
the  cap,  and  in  this  way  he  managed  to  work  the  vein  without  much 
difficulty. 

The  Georgetown  experience  suggested  the  idea  of  adopting  a  similar 
plan  in  the  Ophir.  Accordingly,  Mr.  Deidesheimer  had  a  mortice  cut 
at  the  junction  of  two  caps,  which  were  already  in  place,  and  having  a 
post  framed  with  a  tenon  to  fit,  set  the  post  in  place  directly  above  the 
one  resting  on  the  floor  below.  In  a  short  tim6  four  posts  were  in  posi- 
tion with  the  caps  upon  them  as  below,  together  with  the  frail  2x4 
scantling,  the  office  of  which  was  to  keep  the  other  timbers  from  falling 
down.  The  first  ''  square  set "  timbers,  it  will  be  seen,  were  framed  in 
the  mine,  the  mortices  being  cut  in  the  timbers  in  place.  The  work  of 
extracting  ore  proceeded  slowly  yet,  for  the  ground  had  to  be  secured  as 
well  as  possible.  It  soon  became  evident,  however,  that  something  more 
substantial  than  2x4  scantling  would  be  required  to  keep  the  timbers  in 
position,  and  it  was  determined  to  put  in  timbers  of  the  same  dimensions 
as  those  forming  caps  and  posts.  This  was  done  at  once,  and  the 
"  square  set "  was  complete  in  principle,  though  not  in  detail.  The  caps 
occupied  all  the  space  on  top  of  the  posts,  leaving  no  resting  place  for 
the  "  ties,"  which  had  to  be  supported  in  some  other  manner.  As  they 
were  looked  upon  as  simply  an  auxiliary — a  support  to  the  posts  and 
caps — they  were  only  required  to  be  held  in  position.  Accordingly  a  lot 
of  iron  spikes  were  made,  in  shape  somewhat  like  the  thumb,  having  a 
sharp  point  at  one  end,  the  other  end  having  a  face  three  fourths  of  an  inch 
square.  Two  of  these  spikes  were  driven  into  a  post  at  the  proper  height, 
and  two  in  the  post  opposite,  and  the  tie  placed  so  that  the  ends  rested 
upon  these  iron  lugs,  wedges  being  driven  in  at  the  ends  to  secure  firm- 
ness. The  posts  and  caps  were  now  framed  on  the  surface  and  delivered 
below,  ready  for  use  wherever  needed.  The  work  of  mining  now  pro- 
gressed much  more  rapidly  and  the  problem  seemed  solved.  Soon  after 
it  was  determined  to  frame  the  timbers  so  that  the  ties  might  also  rest 
on  the  posts.  The  stopes  becoming  of  such  great  size,  the  dimensions  of 
the  timbers  were  increased  and  they  were  then  framed  as  shown  in  the 
accompanying  illustrations. 

As  the  work  progressed  slight  changes  were  made  from  time  to  time 
whenever  any  improvement  seemed  possible.  Sills  were  laid  upon  the 
floors  of  the  levels  as  a  foundation  for  the  timbers  above,  which  had 
now  assumed  massive  proportions.  The  sill  timbers  were  cut  as  long 
as  it  was  possible  to  get  into  the  mine.  The  men  who  were  obliged  to 
handle  these  ponderous  timbers  could  see  no  reason  why  the  sills  should 
be  longer  than  the  caps,  and  had  from  the  first  looked  upon  the  growth 
of  this  new  system  of  timbering  with  much  prejudice.  When  the  great 
stopes  were  carried  up  from  level  to  level  the  wisdom  of  the  use  of  long 
sills  became  apparent,  as  they  permitted  the  removal  of  all  the  ore  and 


—  43  — 

the  placing  of  timbers  without  danger  or  loss,  which  could  not  have  been 
accomplished  with  short  sills,  as  when  breaking  up  through  the  floor  of 
a  level  from  below  short  sills  would  have  nothing  to  sustain  them. 

When,  in  the  course  of  ore  extraction,  the  work  reached  the  walls, 
additional  timbers,  called  "wall  plates,"  were  put  in,  as  shown  in  the 
sketch  of  timbering  in  the  Ophir  Mine.  The  caps  were  extended  from 
the  nearest  post  to  the  wall  plate,  except  when  a  post  came  within  two 
feet  of  the  wall  plate.  In  such  case  the  cap  extended  from  the  wall 
plate  to  the  second  post  in  a  single  piece. 

By  a  close  inspection  of  the  drawings  the  details  may  be  plainly  seen. 
It  will  be  noticed  that  a  system  of  braces  reaching  diagonally  across  the 
sets  was  also  introduced,  as  well  as  close  lagging  on  the  walls.  There  is 
no  doubt  that  the  Ophir  was  the  best  timbered  mine  in  the  world,  but 
the  Comstock  miners  who  gladly  adopted  the  Deidesheimer  system  soon 
began  to  disregard  many  precautions  which  to  them  seemed  unnecessary. 
The  diagonal  braces  were  left  out,  and  the  ground  was  found  to  stand 
about  as  well.  Then,  anxious  to  still  further  reduce  expense  and  hurry 
the  work  of  extraction,  the  lagging  on  the  walls  were  dispensed  with,  and 
later,  in  somewhat  firmer  ground,  the  wall  plates  were  left  out,  and 
finally  the  timbers  were  placed  in  rectangular  sets,  with  only  a  few  props 
here  and  there  to  the  walls  and  roof,  as  shown  in  the  drawing  of  the 
Caledonia  Gold  Mine.  The  disregard  of  these  important  details  in 
American  mines  has  resulted  in  numerous  disastrous  caves. 

Owing  to  the  careless  timbering  in  the  "  Big  Bonanza,"  in  the  Cali- 
fornia and  Con.  Virginia  Mines,  cribs  of  solid  timber  had  to  be  built, 
reaching  from  the  floor  to  the  roof. 

The  sketch  of  the  Caledonia  Mine,  in  the  Black  Hills,  S.  D.,  repre- 
sents the  mine  as  it  appeared  in  the  spring  of  1883.  The  main  shaft 
was  sunk  in  the  large  vein,  the  hoisting  works  being  located  on  the  adit 
level,  200  feet  from  the  surface,  vertical  measurement,  and  820  feet  from 
the  mouth  of  the  tunnel.  This  shaft  reached  the  foot  wall  on  the  300- 
foot  level,  and  a  large  stope  was  at  once  opened  around  the  shaft,  a  pil- 
lar of  ore  30  feet  square  being  left  to  support  it.  The  shaft  was  continued 
vertically  to  the  400-foot  level  and  an  extensive  stope  opened  there  also. 
The  gold-bearing  rock  of  the  Caledonia  is  hard  white  quartz,  which 
occurs  in  bunches  and  reticulated  veins  in  chloritic  schist,  and  in  this 
respect  resembles  some  California  mines,  as  the  Utica-Stickles,  Gover, 
and  some  others.  In  the  Caledonia  great  headers  were  excavated  in 
advance  of  placing  the  square  sets.  The  timbers  were  all  properly  framed 
and  were  massive,  but  there  was  a  disregard  of  what  were  considered 
the  minor  unnecessary  details  in  placing  them,  particularly  on  the  walls 
and  against  the  roof.  As  these  large  stopes  were  extended,  too  broad  an 
area  was  taken  out  at  one  time,  and  the  superincumbent  weight  at  length 
threw  the  timbers  out  of  line,  and  almost  without  warning  the  m*ine 
caved,  the  immense  timbers  "jack-knifing"  and  snapping  like  reeds. 
Thousands  of  tons  of  ore,  the  expensive  machinery,  and  a  mass  of 
splintered  timbers  were  dumped  in  a  chaotic  mass  to  the  bottom  of  the 
400-foot  level.  There  were  three  causes  which  led  up  to  this  disaster: 
The  extraction  at  one  time  of  too  large  an  area  of  ground;  carelessness 
in  timbering,  and  the  slippery  nature  of  the  foot  wall  (talc  schist), 
which  afforded  a  poor  support  to  the  large  pillar  of  ore. 

It  is  unreasonable  to  expect  a  frame  of  timbers,  however  strong,  to 
support  the  weight  of  a  mountain  of  rock,  and  for  that  reason  discretion 


—  44  — 


45  — 


—  46  — 


—  47  — 

should  be  used  in  extracting  large  bodies  of  ore.  It  is  hazardous  to 
attempt  to  remove  a  section  more  than  three  or  four  sets  wide  at  one 
time  from  the  floor  of  one  level  to  that  next  above.  A  breast  may- 
extend  entirely  across  the  deposit  or  vein,  but  if  more  than  four  sets  in 
width  are  removed  at  one  time  it  allows  too  much  weight  to  fall  upon 
the  timbers,  and  the  probability  of  a  cave  is  greatly  increased. 

By  taking  out  a  section,  which  may  extend  entirely  across  the  vein  or 
deposit,  three  or  four  sets  wide,  and  carrying  the  stope  up  somewhat  in 
the  form  of  a  pyramid,  so  that  on  nearing  the  floor  next  above  only  the 
space  of  a  single  set,  or  at  most,  not  more  than  two,  be  at  first  removed, 
and  the  timbers  firmly  wedged  to  the  sills  before  enlarging  the  excava- 
tion at  that  point,  all  the  ore  may  be  extracted,  and  the  operation  in 
this  manner  is  attended  by  the  least  expense  and  danger.  When  a 
section  has  been  mined  out  from  level  to  level  as  described,  a  second 
section  may  be  attempted.  Under  all  ordinary  circumstances  it  will  be 
found  that  the  timbers  will  usually  support  the  ground  until  the  stopes 
can  be  filled  with  waste.  At  many  mines  waste  is  obtained  on  the 
surface,  and  in  some  the  opening  of  large  chambers  in  the  hanging 
wall  is  necessary  to  obtain  a  sufiicient  amount  of  material  for  filling 
the  stopes.  There  is  always  danger  in  the  removal  of  a  mass  of  rock 
which  stands  on  a  base  that  is  broader  than  its  upper  portion,  or 
apex,  like  the  letter  "A,"  while  on  the  other  hand  a  ''  V  "  shaped  mass 
is  largely  supported  by  the  walls.  Many  ore  bodies  are  lens- shaped; 
that  is,  broader  at  the  center  than  those  portions  either  above  or  below; 
and  in  these  masses  the  greatest  expense  and  danger  attend  the  removal 
of  the  upper  portion. 

CONSTRUCTION    OF    SQUARE   SETS. 

In  building  square  sets,  the  sills,  16  to  20  feet  in  length,  are  first  laid 
down  on  the  floor  at  right  angles  to  the  walls.  These  timbers  are  the 
largest  in  use  in  the  mine,  and  should  properly  be  as  long  as  they  can 
be  handled.  At  regular  intervals  shallow  depressions  are  cut  across  the 
upper  face  of  the  timber  one  inch  in  depth  and  superficially  the  same  size 
as  the  posts  which  are  to  rest  upon  the  sill.  In  the  center  is  cut  a  mortice, 
two  thirds  the  square  of  the  post,  at  least  QxQj  and  larger  as  the  size  of 
the  timber  is  increased.  Into  the  mortice,  a  tenon  on  the  bottom  of  the 
post  fits  nicely.  The  sills  are  laid  horizontally  and  exactly  parallel,  at 
such  distances  as  may  have  been  determined  upon,  usually  5  or  6  feet 
from  center  to  center  of  the  posts.  The  sets  may  be  placed  in  the  form 
of  squares  or  rectangles.  Two  sills  having  been  laid,  four  posts,  con- 
stituting the  four  corners  of  a  set,  may  be  placed  in  position.  They  may 
be  of  greater  length  than  the  posts  of  sets  above,  the  object  being  to 
afford  more  room  overhead  on  the  sill  floor,  if  desirable.  A  temporary 
platform  is  constructed  by  spiking  stout  planks  to  the  two  sets  of  posts 
at  right  angles  to  the  sills,  and  placing  on  them  planks  or  lagging.  This 
staging  is  built  at  a  suitable  height,  to  enable  the  men  standing  thereon 
to  lift  the  heavy  caps  and  place  the  ends  upon  the  framed  posts.  The 
caps  are  placed  directly  above  the  sills;  that  is,  in  a  direction  extending 
from  wall  to  wall. 

Each  post  is  framed  with  a  tenon  both  top  and  bottom;  that  at  the 
upper  end  being  two  thirds  or  three  fourths,  and  that  at  the  bottom, 
one  third  or  one  fourth  the  thickness  of  the  cap.     (See  the  detail  draw- 


—  48  — 

ings.)     It  is  necessary  that  the  bottom  of  each  post  shall  rest  directly 
upon  the  top  of  that  in  the  set  next  below.     All  the  timbers  must 
carefully  framed  or  it  will  be  found  that  they  will  not  join  properly. 

Having  placed  caps  upon  the  posts,  the  ties  may  also  be  lifted  into 
position,  crossing  from  post  to  post  and  resting  upon  them  in  the  same 
manner  as  the  caps,  but  at  right  angles  to  them.  Ordinarily  caps  are 
broader  on  one  side  than  on  the  other.  The  broad  side  is  laid  upward,  the 
width  of  which  is  equal  to  that  of  the  post,  which  is  square.  The  tie  is 
equal  to  the  smaller  width  of  the  cap.  The  ties  should  fit  tightly, 
and  if  they  do  not,  must  be  secured  by  wedging  at  the  ends.  The 
best  results  are  obtained  when  it  is  necessary  to  drive  the  ties  down  with 
mauls. 

As  the  work  of  extracting  the  ore  proceeds  the  timbering  keeps 
pace  with  it.  As  the  stopes  are  carried  upward,  set  is  built  upon  set, 
reaching  from  one  level  to  another.  Temporary  working  floors  are  laid, 
split  lagging  being  used  for  this  purpose.  These  floors  are  moved  from 
time  to  time  as  the  work  progresses.  Ore  broken  down  on  these  floors 
is  shoveled  into  the  bins  beneath,  or  onto  the  sill  floor  before  the  bins 
have  been  provided,  and  from  there  shoveled  or  dumped  into  cars  and 
sent  to  the  surface. 

When  timbers  have  been  placed  the  wedges  along  the  walls  should  be 
driven  up  between  the  plates  and  walls,  and  in  all  other  places  where 
needed,  to  secure  firmness  and  rigidity,  and  some  one  man  should  be 
detailed  to  look  after  them  and  see  that  they  remain  so;  for  in  large 
stopes  the  ground  is  constantly  shifting  more  or  less,  and  the  weight 
being  transferred  from  one  point  to  another  causes  the  wedges  to  loosen, 
when  they  must  be  again  tightened  to  insure  safety. 

The  size  of  timbers  used  in  the  square  set  system  ranges  from  8x8  or 
8x10  inches  to  20x24  or  even  24x28  inches,  though  timbers  of  the  latter 
dimensions  are  often  difficult  to  obtain.  When  such  massive  timbers 
cannot  be  had,  the  sets  may  be  constructed  on  a  smaller  scale,  having  a 
lesser  distance  between  posts,  and  also  less  height  to  the  set;  thus  greater 
strength  is  secured  by  the  employment  of  a  larger  number  of  timbers. 

Caps  encroach  upon  the  posts  2  to  6  inches  according  to  their  dimen- 
sions, while  ties  have  a  rest  of  1  to  4  inches,  this  being  also  determined 
by  the  size  of  the  timbers.  The  posts  are  framed  in  accordance  with  the 
dimensions  determined  upon,  which  must  be  constant,  to  secure  uni- 
formity, whether  the  post  be  16x16  or  24x24.  As  all  caps  are  of  the 
same  length  and  all  ties  of  an  equal  length,  it  is  evident  that  if  the 
tenons  on  the  posts  vary  with  any  difference  in  the  size  of  the  posts 
(should  any  difference  occur),  the  system  would  soon  be  out  of  line.  As 
the  timbers  used  are  all  sawed,  it  should  not  be  difficult  to  secure  them 
having  a  uniform  size  for  any  single  stope.  In  any  event,  the  tenons  at 
the  top  and  bottom  of  the  post  must  have  a  uniform  size  regardless  of 
the  dimensions  of  the  post.  For  instance,  should  18-inch  posts  be  in  use 
on  any  particular  level,  framed  with  12-inch  tenons,  if  from  necessity  or 
choice  a  20-inch  or  24-inch  post  be  introduced  in  the  sets,  it  must  have  a 
12-inch  tenon,  corresponding  with  the  others.  Square  timbers  are  usually 
framed  with  gang  saws,  and  are  therefore  uniform,  and  any  particular 
stick,  whether  post,  cap,  or  tie,  may  be  used  in  any  portion  of  the  mine. 

Posts  and  caps  which  come  in  contact  with  the  wall  plate  are  mostly 
framed  by  hand,  to  order,  careful  measurement  having  first  been  made 
to  determine  the  exact  dimensions.     Caps  which  meet  the  plate  within 


\ '  ^ 


—  49  — 

less  than  two  thirds  the  width  of  the  set  are  frequently  made  continuous 
from  the  second  post.  Wall  plates  are  cut  in  sections,  the  length  of 
which  is  determined  by  the  conditions  in  the  mine.  These  are  also  mostly 
framed  by  hand.  The  manner  of  framing  and  fitting  these  timbers 
will  be  understood  by  reference  to  the  drawings. 

CAP   SILLS   AND   THEIR   USE. 

Cap  sills  are  often  used  in  preference  to  wall  plates  on  the  foot  wall 
of  a  vein.  They  are  applicable  to  small  stopes  as  well  as  great  chambers. 
As  the  name  implies,  these  timbers  are  simply  an  extension  of  the  cap 
from  the  post  nearest  the  foot  wall  to  the  wall  where  it  rests  .upon  a 
hitch  cut  in  the  wall  (2  feet  or  more,  according  to  the  character  of  the 
ground).  It  then  forms  a  sill  for  the  post  of  the  set  next  above,  as  illus- 
trated in  the  accompanying  drawing. 

AN    IMPROVED    SEAT    FOR   THE    POST   ON    THE    SILL. 

The  method  commonly  in  use  for  cutting  a  seat  for  a  post  in  the  sill : 
that  of  cutting  a  section  an  inch  deep  entirely  across  the  face  of  the  sill, 


THC  FRAMING      FOR  TIES 
PO  ST5  AND     SILLS. 


in  the  center  of  which  is  a  mortise  to  admit  the  tenon  of  the  post,  has 
been  superseded  in  some  mines  by  a  new  practice,  which  has  many 
advantages,  particularly  the  ease  with  which  all  rock  and  other  foreign 
4c 


—  50  — 

substance  may  be  removed  when  ready  to  set  the  post.  The  tie  or  girt 
is  let  in  on  each  side,  they  being  cut  out  to  the  depth  of  one  inch  at  the 
ends.  The  drawing  will  explain  the  idea  better  than  a  description.  The 
posts  have  a  tenon  one  inch  only  in  depth.  A  longer  tenon  would  afibrd 
no  additional  security  or  firmness. 

RECOVERING    LOST   GROUND. 

A  great  deal  of  good  ore  is  sometimes  lost  by  the  settling  of  large  veins 
upon  the  timbers  of  the  first  few  floors  of  a  stope  so  heavily  as  to  throw  th(^ 
timbers  out  of  line,  when  bulkheading  and  filling  in  must  at  once  l)e 
resorted  to,  to  prevent  caving.  In  the  Anaconda  Mine,  of  Butte  City,  Mon- 
tana, a  case  of  this  kind  occurred.  The  timbers  on  the  sill  floor  were  forced 
out  of  line,  and  it  was  evident  that  a  disastrous  cave  was  imminent.  The 
stope  was  packed  full  of  timber  and  waste  as  rapidly  as  possible  and  the 
level  abandoned.  A  drift  was  then  run  from  a  cross-cut  in  the  foot  wall, 
60  feet  from  the  vein,  and  in  this  lateral  drift  at  distances  of  60  feet,  and 
directly  opposite  the  chutes  in  the  abandoned  stope,  as  established  by 
the  mine  surveyor,  a  square  set  was  placed.  A  raise  was  then  carried 
up  on  an  incline  to  the  vein,  where  it  was  still  intact  above  the  filled 
stope  from  each  of  these  points.  These  raises  were  timbered  with  square 
sets,  which  in  section  would  present  the  appearance  of  a  series  of  steps. 
The  rock  in  which  the  drift  was  run  was  solid  granite,  but  as  the  foot 
wall  was  approached  it  was  much  decomposed  and  required  substantial 
timbering.  Had  the  foot  wall  country  rock  been  firm  and  hard  no  timber 
would  have  been  necessary,  except  at  the  stand  on  the  floor  of  the  drift 
where  the  loading  chute  was  constructed  and  at  the  junction  of  the 
winze  and  foot  wall  of  the  vein.  Through  the  winzes  thus  made  the  lost 
ore  was  almost  entirely  recovered. 

DIAGONAL    BRACES. 

These  timbers  are  necessary  in  heavy  ground.  It  must  be  borne  in 
mind  that  they,  in  a  measure,  perform  the  office  of  stulls,  and  should 
not  be  placed  at  right  angles  to  the  hanging  wall,  but  at  a  higher  angle. 
For  instance,  supposing  the  inclination  of  the  hanging  wall  to  be  45 
degrees,  the  diagonal  braces  should  stand  at  55  degrees.  The  height  and 
width  of  the  sets  must  be  determined  by  the  desired  inclination  to  be 
given  the  diagonal  or  angle  braces,  and  before  this  can  be  determined 
the  inclination  of  the  hanging  wall  must  be  known.  The  angle  braces 
may  be  of  the  same  size  as  the  posts  or  a  little  smaller.  These  timbers 
are  not  mortised  nor  framed  with  tenons,  but  are  slipped  in  sideways 
and  secured  by  thin  wedges  if  they  are  not  tight  when  put  in  place. 

SIDE   PRESSURE. 

When  the  pressure  is  greater,  apparently,  from  the  side  than  from 
overhead,  the  method  of  framing  and  joining  these  timbers  is  somewhat 
different.  The  cap  becomes  the  post.  An  examination  of  the  drawings 
will  convey  an  idea  of  the  system  employed  under  these  conditions. 
The  tenons  at  each  end  of  the  cap  in  this  case  are  exactly  the  same  size, 
while  the  tie  is  also  provided  with  a  tenon,  but  of  different  style  from 
that  used  where  the  timbers  are  framed  to  resist  top  pressure.     The 


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f— 

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00 

—  51  — 

placing  of  wall  plates  and  angle  braces  is  the  same  in  each  system. 
The  accompanying  drawings,  showing  a  horizontal  and  vertical  section 
of  a  corner  in  both  the  top  and  side  pressure  systems,  show  plainly  the 
details  of  both  methods. 

BULKHEADS   AND   CRIBS. 

It  frequently  occurs  that  bulkheads  of  solid  timber,  or  cribs  filled 
with  rock,  have  to  be  built  to  sustain  sinking  roofs  which  have  already 
been  substantially  timbered.  Bulkheads  are  formed  by  laying  massive 
squared  timbers  side  by  side,  filling  the  space  between  sets.  Upon  these 
are  laid  a  second  layer  at  right  angles  to  the  first,  and  so  on  from  floor 
to  roof  of  the  stope.  Cribs  are  constructed  by  building  up  timbers  in 
the  form  of  a  hollow  square  or  rectangle,  the  interior  space  being  filled 
with  large  broken  rock,  and  also  extends  from  floor  to  roof.  Either  of 
these  devices  forms  a  very  substantial  support  to  settling  ground,  though 
sometimes  inefficient. 

Bulkheads  of  solid  masonry  are  sometimes  built  in  mine  workings 
to  stop  a  heavy  influx  of  water.  They  should  be  constructed  with  the 
greatest  care  and  in  the  most  substantial  manner  possible  to  prevent 
future  collapse.  When  it  becomes  necessary  to  build  a  bulkhead  of  this 
kind  a  section  should  be  cut  in  the  floor,  sides,  and  roof  of  the  drift, 
and  the  masonry  extended  into  these  spaces.  Water  bulkheads  are 
sometimes  built  of  dry  timbers,  which,  swelling,  effectually  shut  off  the 
influx  of  water. 

An  instance  recently  came  to  the  knowledge  of  the  writer  in  which  a 
large  flow  of  water  followed  the  cutting  of  a  subterranean  reservoir  by 
a  power  drill.  As  usual  in  such  cases,  wooden  plugs  were  inserted  and 
driven  in,  but  to  no  purpose,  the  force  of  the  water  driving  them  out. 
The  protection  of  a  bulkhead  seemed  necessary  to  prevent  the  flooding 
of  the  mine.  An  experiment  was  first  tried,  which,  proving  successful, 
rendered  the  bulkhead  unnecessary.  A  section  of  pipe  provided  with  a 
globe  valve  was  inserted  in  the  hole,  the  valve  remaining  open  until  the 
pipe  was  firmly  secured  by  wooden  braces  and  tightly  wedged  in  the 
rock.  The  valve  was  then  closed  and  the  flow  shut  off.  Provision  then 
being  made  to  handle  the  water,  the  valve  was  opened  partly  and  the 
reservoir  drained.  It  seems  that  this  plan  might  be  adopted  with  ad- 
vantage where  the  influx  of  water  interferes  with  the  construction  and 
completion  of  a  water-tight  bulkhead,  for  at  times  the  flow  of  water  is 
so  great  that  it  is  almost  impossible  to  construct  a  bulkhead,  owing  to 
the  pressure  of  the  water  back  of  it. 

TIMBERING   AT   THE   UTICA   MINE. 

The  largest  known. body  of  ore  in  California  to-day  is  in  the  Utica- 
Stickles  Mine,  at  Angles  Camp,  Calaveras  County.  Its  extent  is,  as  yet, 
unknown.  The  workings  have  thus  far  exposed  a  mass  of  gold-bearing 
rock  ranging  from  40  to  more  than  100  feet  broad,  over  400  feet  high,  and 
exceeding  1,000  feet  in  length.  Stopes  of  this  size  require  a  very  sub- 
stantial system  of  timbering,  and  the  square  set  system,  which  has  been 
described  at  length,  is  exactly  suited  to  its  requirements.  It  is  not  in  use, 
however,  but  in  its  stead  another  system,  which  is  quite  similar,  and 
based  on  exactly  the  same  principles,  still  having  very  important  differ- 


—  52  — 

ences.  A  study  of  the  accompanying  timber  sketch  of  the  Utica  Miiu" 
will  suffice  to  make  an  understanding  of  the  method  plain. 

The  timber  used  in  this  mine  is  exclusively  round,  peeled  pine  logs, 
which  are  delivered  by  contract  at  the  surface  works.  The  cost  of  these 
logs,  I  am  informed,  is  10  cents  for  each  inch  of  diameter,  making  ;i 
16-foot  18-inch  log  cost  $1  80,  and  a  24-inch  log,  $2  40.  These  timbers 
are  all  cut  into  two  lengths  of  8  feet  each.  They  are  mostly  over 
18  inches  in  diameter,  and  occasionally  are  found  as  large  as  28  and  80 
inches  in  diameter.  The  posts  are  framed  to  14  inches,  top  and  bottom. 
the  tenon  being  4  inches  high.  Caps  are  framed  to  14  inches  at  either 
end,  the  tenon  being  6  inches  long.  Thus  it  will  be  seen  when  two  adja- 
cent caps  are  placed  on  a  post  the  tenons  will  not  meet,  but  will  have  a 
2-inch  space  between  them.  This  space  is  filled  by  driving  in  a  section 
of  2-inch  plank  14  inches  square.  At  the  junction  of  caps  and  posts,  it 
will  be  noticed,  are  two  ties  in  place  of  one,  as  in  the  square  set  system. 
These  ties  range  from  a  foot  to  1 6  inches  in  diameter,  and  are  about  4 
feet  in  length.  The  lower  one  has  a  horn  4  inches  in  length  on  its  upper 
half.  These  projections  rest  upon  the  shoulders  of  the  posts.  The  upper 
tie  is  tightly  wedged  between  the  posts,  as  shown  in  the  drawing.  This 
system  has  replaced  that  formerly  in  use  at  the  Utica  Mine,  in  which 
the  posts  were  16  feet  high;  caps  being  let  into  the  sides  at  8  feet  and 
others  resting  on  the  top.  The  new  system  is  much  preferred  and  has 
many  advantages  over  the  old  (a  30-inch  post  16  feet  in  length  weighed 
over  3,300  pounds).  In  the  present  system  the  posts  and  caps  weigh 
from  700  to  over  1,000  pounds  each. 

Owing  to  the  impossibility  of  procuring  round  timbers  that  are  exactly 
uniform  in  size,  the  Utica  system  involves  a  vast  amount  of  dressing 
timbers  underground  to  secure  the  necessary  uniformity  in  joining. 
While  the  system  is  one  affording  great  strength  when  properly  placed, 
it  would  seem  to  possess  no  advantages  over  the  square  set  system,  and 
to  be  more  troublesome,  cumbersome,  and,  in  the  writer's  opinion,  more 
expensive  than  the  latter,  though  the  first  cost  of  round  timber  is  less 
than  that  of  sawed  square  timber. 

No  wall  plates,  excepting  short  single  pieces,  are  employed,  and  no 
sills  are  laid  upon  the  levels  of  the  floors.  It  would  appear  that  neglect 
to  provide  sills  will  in  time  prove  a  great  disadvantage  in  connecting 
the  stopes  from  level  to  level. 

HANDLING   TIMBERS. 

The  manner  of  handling  timbers  at  mines  depends  to  a  great  extent 
on  the  size  and  number  of  timbers  used,  and  on  the  character  of  the 
shaft,  whether  it  be  vertical  or  inclined.  In  drift  mines  and  mineral 
deposits  which  lie  nearly  horizontal,  they  are  sent  in  on  flat  cars 
(trolleys)  built  for  the  purpose.  When  cages  are  used  in  vertical  shafts 
the  timbers  are  set  upright  on  the  floor  of  the  cage,  lashed  together, 
and  lowered  into  the  mine.  At  inclines  it  is  a  common  practice  to  load 
the  timbers  into  the  skip  and  lower  them  down  the  shaft  in  that  way 
to  the  desired  point. 

At  the  Utica  Mine  the  heavy  timbers  are  handled  quickly  and  easily 
on  the  surface.  They  are  sent  from  the  framing  machine  to  the  shafts 
on  trolleys.  Two  men  are  kept  busy  a  great  deal  of  the  time  in  sending 
timbers  underground.     A  number  of  stout  chains  8  feet  in  length  are 


—  53  — 

jtrovided.  In  the  center  of  each  chain  is  a  4-inch  ring,  and  at  each  end 
a  (log,  having  a  point  projecting  at  about  70  degrees  4  inches  in  length. 
One  of  these  dogs  is  driven  into  the  side  of  a  post  or  cap  somewhat 
al)0ve  the  center.  The  chain  is  passed  over  the  end  of  the  timber  and 
the  other  dog  is  driven  into  the  opposite  side.  A  spike  6  or  8  inches 
long,  having  a  5-foot  piece  of  rope  attached,  is  driven  well  into  the  lower 
end  of  the  timber,  and  it  is  ready  to  lower  into  the  mine.  Beneath  the 
skips  are  stout  chains  with  rings.  An  extra  chain  having  hooks  at 
the  ends  is  at  hand.  This  forms  the  connecting  link  between  the  chain 
1  leneath  the  skip  and  that  attached  to  the  timber.  Having  been  securely 
hooked  the  skip  is  raised  slowly,  lifting  the  timber  from  the  platform. 
The  rope  and  spike  at  the  bottom  are  used  to  bring  the  timber  to  a 
standstill  before  the  skip  is  lowered.  Having  reached  the  level  where  it 
is  wanted  the  rope  again  comes  into  use  in  landing  the  timber  at  the 
-lation. 


CL-CViCC      FOR 
LOWERINC     TJMSCR 

j  UNDER      TME 

'        CAGC     OR      SKIP. 


The  Utica  shaft  is  almost  vertical.  This  process,  while  a  convenient 
and  quick  way  of  handling  these  heavy  timbers,  cannot  well  be  used  in 
shafts  departing  very  far  from  the  perpendicular,  unless  a  slide  of  plank 
be  laid  between  the  guides  or  runway  of  the  skip,  and  it  would  then  be 
advisable  to  line  the  slides  with  strips  of  flat  iron.  It  would  appear 
that  timbers  might  be  handled  in  this  manner  in  shafts  having  as  low 
an  inclination  as  35  degrees,  particularly  if  the  slide  be  lubricated.  It 
is  certainly  a  superior  method  to  that  of  loading  the  timbers  into  skips. 


—  54  — 

wh*  jh  involves  much  difficulty,  particularly  in  landing  them  at  stations. 
Most  mines  have  blocks  and  tackle  at  the  stations,  secured  to  heavy 
timbers  overhead,  for  unloading  timbers  from  skips. 

It  is  always  a  good  plan,  where  possible,  to  have  complete  connection 
from  level  to  level  by  means,  of  winzes  in  veins  requiring  very  large 
timbers.  The  timbers  may  then  be  unloaded  on  the  level  above  where 
they  are  to  be  used  and  lowered  through  the  winze  nearest  the  stope 
where  they  are  to  be  placed,  and  to  the  particular  floor  of  the  stope 
where  they  are  required.  Winzes  for  this  purpose  should  have,  if  possi- 
ble, an  inclination  of  65  degrees.  Where  the  slope  is  too  low  for  them 
to  run,  however,  the  timbers  may  be  dragged  down,  which  is  certainly 
much  cheaper  and  easier  than  hauling  them  up. 

All  timbers  should  be  framed  on  the  surface  where  possible,  as  it  saves 
much  time  and  trouble.  Gang  saws  are  much  to  be  preferred  to  any 
other  method  of  framing  timbers  for  square  sets.  The  timbers  can,  in 
this  way,  be  framed  as  exactly  if  not  more  so  than  by  hand,  and  in  one 
tenth  of  the  time. 

In  mines  where  cages  are  used,  when  it  is  necessary  to  send  long  tim- 
bers down  into  the  mine,  as  sills  for  square  sets,  or  long  plates,  much 
time  is  saved  by  boring  an  auger  hole  through  the  timber  near  the  end 
and  passing  an  iron  bar  (|-inch)  through  it.  The  ends  of  the  bar  are 
provided  with  threads  and  nuts.  These  ends  pass  through  the  ends  of 
a  U-shaped  frame,  forming  a  large  clevis.  The  clevis  is  attached  by  a 
chain  to  the  bottom  of  the  cage,  and  in  this  manner  lowered  to  the  point 
desired.  The  principle  is  the  same  as  that  employed  at  the  Utica  Mine. 
The  drawing  on  page  53  will  convey  an  idea  of  the  device  above 
described. 


INDEX 


A 

Page. 

Alma  shaft,  Jackson,  Cal 21-27 

Aiuiconda  Mine,  Montana .- 50 

Angle  braces,  in  square  sets 50 

Angles,  taking  in  shafts 27 

Lionaut  inchne,  Jackson,  Cal. 27 

B 

]'>ark  on  timbers .-. -. 9 

liedrock,  swelling _ -- 14 

r.eveled  notch,  the _ - --  9 

I'.i-metallic  Mine 34 

"  r.locky  ground  " _ 15 

r>olts  and  dogs  for  hanging  shaft  timbers _ 19 

I'.owlders  from  roof - 15 

IJraces,  diagonal 50 

r>reast  boards,  method  of  using.. .- - 24^25 

r.reasting  caps 7-9 

liuehanan  Mine,  Tuolumne  County 36 

JUilkheads  and  cribs  for  support  01  roofs 51 

lUUkheads,  water-tight - 51 

C 

ssons,  where  used 26 

averas  Consolidated  tunnel,  timber  in 7 

edonia  Mine,  timbering  of -. 43-44-45 

'   iiifornia  mines,  square  sets  in 38 

Caps  and  posts,  in  drifts. - 9 

In  square  sets 48 

Size  of... 12 

Careless  timbering,  in  Caledonia _ '. 43,44 

In  Con.  Virginia _ _ - 43 

Chambers  and  stopes _ _ 27 

Chambers,  great _ - 38 

Chutes  or  ore  slides __- --  32 

Chutes,  loading,  in  drifts _ 32-36-37 

In  shafts .- —  32 

Clay  linings  for  shafts... - --  26 

Comstock  shafts 21-22-23 

Cottonwood  for  timbers 6 

Cribbed  shaft  ... - 17 

Cribs  and  bulkheads _ 51 

D 

Deidesheimer's  square  sets 39 

Diagonal  braces - - ---  50 

Dividers  in  shafts.... - 20-21-24-25 

Dogs  for  hanging  timbers - 19 

Drainage,  importance  of - 

Drains - 

Drift  mines,  timbering  in 

Drift  of  Kennedy  Mine,  timber  in 

Drifts  and  tunnels 

E 
El  Capitan  shaft,  Nevada  County,  Cal — 

F 

False  sets 

Fissures,  precautions  with.. 

"Forepohng" 

Forman  shaft,  Comstock  Lode --- 


—  56  — 

Page. 

Framing  of  shaft  timbers 19-22-23 

Of  drift  and  tunnel  timbers 9 

Of  guides  in  shafts  -_ 26-27 

Of  square  set  timbers ...46-47-48-49 

Freezing  quicksand  and  watery  ground 26 

G 

Golden  Gate  Mine,  Sonora,  loading  chute  in  shaft  of 38 

Gover  Mine,  timber  tests  in G 

Great  chambers  and  square  sets 38 

Guides  in  shafts 26 

H 

Hanging  bolts  and  dogs  for  shafts 19-20 

Hanging  bolts  and  dogs,  manner  of  using _.  19-20 

Hanging  wall,  timbering  a  soft _ 27 

Handling  timbers,  on  the  surface  at  Utica  Mine 52 

Handling  timbers,  underground  _. 52 

Honduras  Mine,  timbering  in , 6 

I 

Inclines 27 

Timbering 27 

Argonaut,  at  Jackson,  Cal. 27 

Iron  dogs  for  hanging  timbers 19 

K 
Kinds  of  timber  used  in  mines 6 

L 

Lagging,  how  made 10 

In  drift  mines.. 7 

Kinds  of  wood  used  in  making 12 

Manner  of  driving  in  drifts 10 

Manner  of  driving  in  shafts 10,24-25 

•    Size  of  shafts -  10 

Levels,  connecting 34 

Loading  chutes,  manner  of  constructing... 32 

In  drifts... 32 

In  shafts 36,37 

Square  sets 38 

Long  wall  system 29 

Lost  ground,  recovering _ 50 

Lowering  timbers 53 

M 

Manner  of  stoping  large  ore  bodies '^ 

Measuring  distance  between  walls -'7 

N 
New  Almaden  Quicksilver  Mine,  timbering  in i'7 

O 

Oak  for  timbers 6 

Ophir  Mine 43 

Ore  bins 38 

Orp  Rhont, 34 

•r  chutes 36,37 

toping ''^ 

P 

jtall  system 29 

re  to  support  roof --  29 

trcaps ---  5) 

II  joint 12 

are  set ...: 47  48 

t 7  9 

•ifting  cap 9 

)f  timbering  mines 5 


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